Yeah, Mold Breaker status moves are interesting but are relatively niche. Spore/Toxic + hazards that can't be blocked by abilities is not that much.I dunno does Mold Breaker Spore necessarily accomplish a lot? That's an honest question, because when I think Spore being thrown around I think of Grass types that just absorb it. but that's not by ability, that's by typing.
I know there's some relevant abilities, Magic Guard and Overcoat and so forth, but I don't know how much those come up these days.
If anything, it's silly that the new ability is weaker than Mold Breaker for no reason. On a presumably defensively-oriented Pokemon, ignoring abilities on attacks does not make that much of a difference. There are not many useful applications of negative priority status (safe Baton Pass and PP stalling Defog/Heal Bell are all I can think of), so it mostly just slightly worsens the ability. Even if Mold Breaker is considered thematically inappropriate, it's still better to just make a direct clone than it is to tack on the pointless changes. It's just more bloat.