on top of bounce, topsy also loses to substitute. so prank tail glow for example, has NO counters. where imposter can at least catch it before it makes a sub.
the arguments of keeping imposter has been restated so much that there's really no point in restating. however i will throw it back out that without imposter, pokemon have 0 restriction on move sets. tail glow sweepers can easily run perfected coverage, forcing you to use mediocre counters just to stop them. say for example...prank arceus with tail glow, aura sphere/substitute, nature power, and earth power/dark pulse. nothing in this meta can be considered a consistent counter to this, especially when the only moves that even outspeed nature power are fake out and espeed, which is simple as hell to stop, and can still easily break past 99% of teams. imposters presence is enough to force people to think before creating such a mindless threat, forcing them to find a counter, and thus, can restrict their teambuilding options greatly in a way that isn't negative for this meta and actually promotes you to do more then just spam contrary, or spam simple. have you ever questioned why simple spam/contrary spam is stuck in the low ladder? its because mindless spamming of moves should be punished. and although imposter could be considered the same, its up to your OPPONENT to wisen up about their synergy so something like that doesn't happen. you can argue all you want about unaware, but unawares purpose is to stop ALL setup sweepers, and that involves you having to run 2 UNAWARE users otherwise your physical mm2x with simple swords dance, extreme speed, drain punch and knock off has a field day on their specially defensive unaware wall
what does imposters ban accomplish for this metagame that is GOOD? and i'm not asking what the ban would stop. i'm asking how it would be healthy for the meta game. because all it does is promotes overkill power and coverage and no restriction sweepers. which is obviously bad. that's really a no brainer. theres a reason the ability clause is a thing, and thats because "repeating the same process on something tends to give results" 2 setup spammers can easily take on this entire meta togeather if its not just for imposter blocking their fullest potential. it would lead us to eventually banning setup moves altogeather. since having 6 setup mons would become the norm, and would completely erase EVERY team archeotype. prankster? ones pranktaunt/sub. unaware? ones mold breaker, fakespeed? yeah, have fun breaking that steel type. and then what? i already ran through all three potential stops to setup spam. and there are still 3 more waiting for you. heck, you can even combine some of these sets. dislike unaware/pranktopsy? prank rayquaza can easily taunt both then tail glow oblivion to victory. so wheres the other 3 counters to setup spam? dont forget you still need a check to fakespeed...and smashing fakespeedburst.