I'm gonna have to disagree with you here. From playing with certain smeargle builds over the past couple of days it's problem isn't it's frailty. It's a setback, yes, but focus sash gives you an oppurtuinitys to set any hazards you like at least once. Not to mention it's vary rare for a team to have all above 273 speed, so it's very likely it has the capability of setting at least 2 layers at a given moment in a match. In fact, its problem is more so it's lack of offensive prowess.Smeargle's main problem IMO is it's frailty. Its required to run Focus Sash or else it gets one shot by pretty much anything. (In addition to its low base 75 speed) The only time Sticky Web has ever "kicked off" in a meta was RU when Shuckle was allowed. What made Shuckle different was its bulk (Which was complimented by the Sturdy ability, pretty much making it so it didn't even need Focus Sash to get off a Web, and as such, it can run Mental Herb to bypass Taunt/Encore/what have you) and incredible support options. Because of its attributes, the RU ladder was pretty much filled with Sticky Web teams to the point of overcentralization, resulting in Shuckle's ban.
Still, Smeargle Webs isn't necessarily a bad playstyle. You're pretty much required to run Skuntank with it though because of Xatu. (Any other viable Pursuit trapper works as well) A hazard remover of your own is a nice choice due to the fact that your team will likely be worn down quickly. (Spinners over Defoggers as Smeargle will really only be able to get Rocks/Webs up once per game and Defog pretty much removes your effort entirely; Claydol's what I use personally) A Pokemon that isn't reliant on Webs to outspeed stuff is also really good. There are several Wallbreakers that are good when paired up with Sticky Web, such as the also recently dropped Aggron, Aurorus, and Abomasnow. (There are several others as well, but these are the only ones I can think of off the top of my head)
From playing with smeargle, it was hugely difficult to play against something that was faster with substitute or even something as simple as settup Sweepers + Sleep Fodder. Smeargle doesn't have a viable way of damaging the opponent, and spore is its only outlet to not be constant settup fodder. That being said, smeargle does keep momentum quite well because hazards in themselves gain momentum. It's very much so a settup hazards and sack mon, I just wanna emphasise that it's not really it's frailty that's hurting it, but in fact it's lack of damaging attacks.
Also you state that you need a pursuit trapper for smeargle to work all the time and this definitely isn't the case. Smeargle can often find the room to run Skill Swap and take away a Xatus magic bounce at any given moment. Giving you free reign to settup 2 layers of whatever hazards you want should you predict correctly should the xatu not outspeed. And finally I can only ever see smeargle used on the most hyper of hyper offensive builds. An advantage to using these builds is the fact you can keep up the pressure of defoggers / spinners / hazards removers through offensive pressure. A good hyper offensive team won't give the oppurtuinitys for hazards control to do what they do, and if they do, the hyper offensive team should punish you for it. Defog Detterent in Pawniard / Spinblocker in a given Ghost Type, u very much so oversimplify removing hazards vs smeargle offense, because they will almost certainly carry Pawniard and Ghost to pressure hazards removers, and if either is unavailable, the pure offensive pressure of settup sweepers and various wall breakers should be enough.
Agreeing that smeargle webs isn't the greatest playstyle, but it's very good if you give it room to do what it needs to do, and very much so makes mons with levitate a huge advantage to have to play against them.