when garchomp was legel in gen IV, this was pretty much every team:
garchomp/garchomp counter 1/garchomp counter 2/garchomp counter killer 1/garchomp counter killer 2/tyranitar
that was your team, if you didn’t run it, you lost, this is boring, so instead, they banned garchomp and the metagame was soooooooooooooooo much better, there was variety, every kind of playstyle was viable, it was fun, you could run pretty much anything you wanted and have great success
this is basically what mega kangaskhan is doing, you need to run either run mega kangaskhan or mega lucario/ghost with wisp/talonflame/stealth rock user/filler/filler or get swept by him, this is boring and not worth it, yes, he can be beaten but you literally need to make an anti-mega kanga team to do so
this was the same problem with blaziken, you either gave in or ran an anti blaziken team (like my first team who literally made blaziken his bitch) and get swept by some other shit
mega gengar is a whole other beast that was probably the most broken thing in the game, there was literally nothing you could do to stop it if he predicted right
smogon decided that latias and latios might not be so bad, so why not let them down without soul dew and see how it goes, latios got rebanned pretty quickly but latias stayed as it was the biggest check to salamence, which that game eventually became salamence/latias/scizor/heatran/filler/filler so once they banned latias (as it was the bigger problem), salamence had no worries and eventually banned him, and lo and behold, the metagame was fun and balanced again, running a lot options, etc.
it’s better to ban things early than it is to let them linger as it allows for a much faster growth in the metagame, this is why blaziken, mega gengar, and mega kanga (eventually) are banned on smogon, instead of figuring out how to counter those pokes, we can develop a much more balanced metagame that doesn’t have a certain style or pokemon to dominate, if deemed okay, they will unban the pokemon and see if the pokemon isn’t as big of a threat
but don’t bring up gen V, a lot of wish that we can erase that gen from our minds, for some reason smogon never banned drizzle as that was the biggest problem with the gen (they were literally banning everything that abused it like swift swim, thunderus-I, tornadus-T, manaphy, and keldeo was on deck to be suspected), but that’s in the past and now we don’t have to worry about the weather wars as much, which already has created a much more balanced metagame
i would assume shield dust would block the effects of PuP, but the pokemon that learn it are all OHKO’d by return anyways so it’s a pretty moot point, especially when their hidden abilities are way better than shield dust (venomoth gets tinted lens and dustox and vivillion get compound eyes)