Drifloon is almost certainly a top tier threat at this point, but I do not believe it is any more difficult to manage than other top tier Pokemon. Although I would probably have voted for a ban back in March, we've had plenty of time to play around with its checks since then. Let's go over the major arguments for Drifloon's ban so that I can explain why I think it's just fine.
Drifloon's combination of ability and unpredictability is too much.
Recyclefloon's strengths
Drifloon outspeeds the entire relevant metagame after Unburden, which it can activate easily with Substitute. It then outstalls the lucky Pokemon that it's up against the vast majority of the time, burning the enemy to cripple their damage output before mashing Recycle until Drifloon comes out on top.
And then what? And then it's at around half health and easily forced out or revenge-killed, and will likely be unable to do much more than burn things for the remainder of the match if the opponent has even a single Pokemon that can beat Drifloon 1v1, because Drifloon needs to use Recycle to reactivate Unburden from here and that gives the soft Drifloon check a free switch. If it's a more offensive team, then Drifloon won't even be able to do that, because pretty much everything on offense can do over half of Drifloon's health, considering how its bulk is actually a little bit worse than slow Mienfoo without its Eviolite.
This is before considering that hard checks and even outright counters do exist. The standard Drifloon set that we're considering for its ban consists of Substitute / Will-O-Wisp / Acrobatics / Recycle; when your offensive presence consists of burns and 12 Atk Acrobatics, there are bound to be quite a few Pokemon that wall you. These aren't exactly bad Pokemon in their own right, either - Ponyta, Magnemite, and Chinchou have all been fantastic Pokemon since 2014 or earlier. (They're all weak to Diglett, but I'll get to that in a bit.) Drifloon's combination of strengths is incredibly difficult to play around against an unprepared player; even against someone with experience, it's not a dead weight. But how is this different from all of the good and great sweepers we have available - other than that we haven't given Drifloon as much time to be adapted to?
Of course, Drifloon can afford to ditch Substitute for Knock Off or something else that lets it cripple would-be checks. This isn't a bad idea by any stretch, as it allows Drifloon to support its teammates in even more ways. However, it makes Drifloon's 1v1 capabilities much less impressive. Suddenly, it can no longer reliably activate Unburden, which is a pretty big deal when most of the complaints about its brokenness rest on it being able to burn the enemy or heal itself up before the opponent can react. Opposing Knock Off users can quickly take it out. Status users are able to easily cripple it. It really doesn't want to take chip damage early on in most scenarios (unless you need it to put it into Unburden range from Stealth Rock), making it even more of a one-time use support Pokemon than before.
Calm Mind Drifloon isn't its dominant set, but still has what it takes to be an effective sweeper; teams that lack a good CM Drifloon check tend to get swept very badly, and for these match-ups alone I believe CM Drifloon is worth considering. But when we compare CM Drifloon to other notable sweepers, we can see how match-up based it is. Teams that do have a good way to deal with it are almost playing on a 6v5 advantage. The fact that it can get hard walled is a pretty big disadvantage compared to, say, Timburr or Shellder, which can Knock Off something or take out a third of a check's HP right off the bat. Ditching Will-O-Wisp for a coverage move to deal with this neutralizes most of Drifloon's sweeping potential by giving it far less set-up opportunities and leaving it badly damaged by physical Pokemon that can take a + 1 Shadow Ball, which is just about all of them that carry Eviolite.
I don't like the comparisons to Mienfoo claiming that Drifloon's strengths set it apart at all; they fail to consider that Mienfoo has its own strengths that are easily on par with Drifloon's, and I would confidently argue are even better. Drifloon absolutely has the resilience, the versatility, the speed and the sick burns to hassle even the most solidly built teams, but it lacks something vital in such an offensive metagame - offensive presence. Whittling the opposition down with burns is great if they can't hurt Drifloon, but it just doesn't cut it against decent switch-ins. The most offensive Mienfoo variants are able to hit twice as hard with High Jump Kick as itemless 14 Atk Drifloon's Acrobatics; even defensive Mienfoo sets frequently carry High Jump Kick, which hits about 1.5x as hard as itemless Recyclefloon's Acrobatics. Another important advantage for Mienfoo is the momentum that Regenerator + U-turn brings, which is much more effective over the course of the match than a healing move that takes up a turn and only works when some conditions aren't in place; surely this is not a point in favour of Drifloon's survivability.
Drifloon's unpredictability
Unpredictability, what does this mean? Drifloon has several mostly unique sets; between these, there are also minor variations. As a result, only a select few Pokemon can claim to genuinely counter Drifloon.
The main balancing factor here is Drifloon's lack of initial power. It's true that Choice Scarf Chinchou will only serve as set-up bait if it stays in on a boosted CM Drifloon. However, because of CM Drifloon's only decent damage even at +1, and, more importantly, the existence of Normal-types, there is almost no risk to going to a physical Drifloon check to begin with before switching to a CM Drifloon check if need be. Compare this to, say, a Poison Jab Mienfoo lure; a Cottonee coming in looking to tank a weak Knock Off is going to be in for a lot more than the 65 or 80 BP move off 12 SpA that CM Drifloon initially has to offer.
Drifloon can still cripple switch-ins, as Magnemite and the aforementioned Chinchou generally aren't too fond of losing their item to Knock Off. With that being said, they are still able to beat Knock Off Drifloon without much trouble after switching in. This means that although hard counters are few in number, it's not difficult at all to find a hard check. And although you'll be put in a tight spot if Chinchou or Magnemite is your only check to Flying- and Water-types, offensive strategies like this aren't unique to Drifloon; the tried and true bird and fish spam cores are just as capable of producing the same effect.
Drifloon is able to get around traditional bird checks.
Remember when you could fit a Pawniard and an Archen onto your team and say it was fine against birds? Judging by this thread and other discussions, it looks like most of us do. It's not a hard argument to see for people who are just getting back into LC, as many of the teams that were somewhat solid during early ORAS have a great deal of trouble breaking through Drifloon.
But consider this: what if Carvanha or Mienfoo or even Porygon was discovered today? Between its relevant coverage moves, Carvanha as a whole is impossible to wall when it doesn't simply fall back on Destiny Bond, allowing it to easily get through traditional Water-type checks; it's also a huge menace to hyper offensive teams thanks to Speed Boost helping it get around traditional Choice Scarf revenge-killers, its raw damage output that cleanly OHKOes most offensive Pokemon, and its Aqua Jet which picks off weakened priority users. Mienfoo has the extra slots to break a traditional Fighting-type check of its choosing, and can just U-turn out of the rest of them to gain momentum. Porygon has the bulk, utility, and recovery to function as a wall, but at the same time has the coverage and damage output to put many strictly offensive Pokemon to shame.
These are Pokemon that most of us will agree are not banworthy (though there are exceptions). The main difference between them and Drifloon is that we have been dealing with Carvanha/Mienfoo/Porygon for years, whereas it was only over the past few months that Drifloon has been elevated from a fun Pokemon to express your creativity with to a legitimate threat that should be considered in teambuilding. Drifloon may have some fantastic traits, but just as Carvanha and Porygon and Pawniard do, it has its drawbacks as well. It may be dominant, but it is not unusually dominant.
Drifloon also has its fair share of checks that traditional birds do not, mostly stemming from the physical set's lack of offensive presence. Fletchling and Vullaby wish they could beat Pawniard or Archen the way Reyclefloon does, but they are also not PP stalled to oblivion by Rest Munchlax, or any Rest user with better bulk than 23 HP/15 Def that isn't weak to Flying-type attacks, really. They also aren't a free switch-in for Ponyta or Magnemite the way Drifloon is.
Drifloon does get around many traditional bird checks, but that's because it's not a bird, it's a balloon. Add it to your threat list accordingly, and chances are it won't seem so overwhelming after all.
Drifloon synergizes well with Diglett.
A few months ago, Heysup and I were discussing floondig. I argued that floondig is much better than fletchdig because the set of Pokemon that Drifloon handles synergizes better with what Diglett traps, so floondig can beat a greater variety of threats. But Heysup's response helped to change my mind: Drifloon does not have U-turn. This seems trivial until you take into account how difficult it is for Diglett to actually trap key threats without it. Without U-turn, the opponent can just switch their Diglett-weak checks into Drifloon and use moves that Diglett can't come in on. Revenge-killing isn't enough because they can preserve their Drifloon checks by sufficiently weakening your Pokemon instead of outright KOing them, and, if applicable, boost their Speed once they're in play. Double switching Diglett in is extremely risky, and has a good chance to end up with a dead Diglett if the opponent is thinking one step ahead or simply decides that they would rather sack whatever they currently have out; a successful double switch doesn't even have a reward if you aren't sure about the Drifloon check's specific set. Of course, Fletchling's U-turns aren't exactly risk-free either due to its low bulk, but this is still a very notable distinction between floondig and cores like fletchdig and foodig.
But wait a second - Drifloon has Baton Pass! Could that make up for its lack of U-turn? It definitely helps in getting Diglett onto the field, but I mentioned earlier that running Knock Off over Substitute limits Drifloon's capabilities as a standalone threat. Baton Pass is even more extreme in this regard. It almost forces Drifloon to be run alongside something that appreciates specific Drifloon checks gone, and you still have to figure out the Chinchou variant beforehand because of the lack of U-turn chip. As a supportive set, it arguably isn't actually better than Knock Off Drifloon.
This also ties into Drifloon's lack of offensive presence. Trapping something for Drifloon simply isn't as rewarding as doing so for, say, Shellder or Magnemite. Drifloon is often too reliant on burns to deal damage for it to pull off a sweep; bringing down one Pokemon will leave it in revenge-killing range from the next. Floondig is still an excellent supporting core, but dedicating two slots to support is a pretty big commitment, especially when considering floondig's average defensive utility.
Drifloon is similar to banned Pokemon mechanically.
It looks like there's a split on whether this is worth considering for Drifloon's ban, so I'll just go through the key points.
Yanma
A major factor in Yanma's ban was its Hypnosis set, which, like Drifloon, was a support set relying on status. The difference is that Yanma had a Life Orb Speed Boost set that was just as crucial. If it was just the Hypnosis set, then Yanma could be easily checked with RestTalk users. Not so much when most of these RestTalk users were 2HKOed by a Life Orb set. It also went the other way around; checks like Archen that could deal with the Life Orb set were shut down by an accurate Hypnosis.
It's pretty clear why an equivalent offensive Drifloon set does not exist. On top of its average offensive stats, Drifloon's most powerful STAB moves require it to not have an item or its opponent to not be statused. In addition, although Drifloon does have several unique sets, they do not take advantage of each other to the extent that Life Orb and Hypnosis Yanma did.
Swirlix
This comparison hasn't been brought up much in this thread, but I've seen it mentioned in other discussions. Swirlix and Drifloon may both have Unburden, but Swirlix's ban can be summarized in two statements, both of which Drifloon only meets half way.
a. Swirlix had two drastically different sets with huge sweeping potential that could almost immediately break through the other's checks (on top of a decent third set). Most of Drifloon's sets aren't great at sweeping, and even its CM set isn't any more effective than other available sweepers. All of its sets require multiple turns before they can take advantage of another's checks.
b. Swirlix was able to get around any would-be check by switching up a coverage move with almost no cost to its overall ability. Changing a move to get rid of a check significantly hampers Drifloon's 1v1 and/or sweeping potential.
Gligar / Meditite / Misdreavus / Murkrow
When it comes to versatility, Drifloon can go toe to toe with any of these Pokemon. But these four Pokemon weren't banned for their versatility; it was just what helped to push them over the edge. The primary reason all of these Pokemon were banned was for their offensive presence, whether it was their wall-breaking prowess or their sweeping potential. Gligar had a supporting option for every one of Drifloon's, but more importantly, both Sub SD and Koff SD had ridiculous 6-0ing potential even against teams with Gligar checks. Meditite's coverage moves would mean nothing without its powerful STABs coming off a Huge Power-boosted Attack stat. Misdreavus was banned almost solely because its Nasty Plot set, which had about three viable checks if it was HP Fighting and a different three checks if it was Dazzling Gleam. Dcaekrow was up there as one of Murkrow's best sets, but a good amount of its effectiveness stemmed from taking advantage of Life Orb Murkrow's switch-ins. At the end of the day, it was the Life Orb set which let Murkrow 2HKO defensive threats with Brave Bird and OHKO offensive threats with Sucker Punch that contributed the most to its ban. Similarities in terms of mechanics or playstyle are pretty meaningless out of context.
Drifloon is unfun to play against.
I can't really argue against the claim that Drifloon is unfun for the same reason why this question isn't asked anymore in suspect tests. If you think Drifloon is unfun, then there isn't much else to say; it doesn't matter whether it's because Drifloon gave off a bad first impression, or you really liked an early ORAS team, or eww madokooties. I personally feel Trubbish is unfun because it reminds me of
trash's rengar in league. That doesn't mean we should ban Trubbish; it means I should ban rengar when I play with trash. Although discussions about whether a Pokemon is broken or uncompetitive are subjective enough to leave room for debate, they are still grounded in facts; that's why we can look at future suspects and try to compare them to previously banned Pokemon or current key threats.
I just don't think it's a good idea to base whether we ban a Pokemon on whether a theoretical metagame without this Pokemon might be more fun; my theorymonning abilities in early ORAS certainly didn't notify me of Recycle Drifloon becoming a top tier threat.
(By the way, I didn't intentionally coordinate this post with berks, but I think they go well together because he mostly covers Drifloon's checks and I go into detail on its flaws!)
e: I was told that this wasn't clear, but my post is against Drifloon being banned. I'm discussing why I don't agree with the key arguments being brought up in favour of a Drifloon ban.