Giving my thoughts about the whole "please quickban" thing.
Okay. I think people overstimate this thing's potential. A lot. While I can't deny Gallade is a fearsome wallbreaker, its far from perfect and its not really unhealthy or broken, neither restricts teambuilding. For starters, Psychic-, Ghost- and Flying-types are pretty much a must in a meta with so many threatening Fighting types. The playstyle Gallade truly shines against is balance, since it gets more opportunities to switch in and do its job as a breaker. Versus more Offensive playstyles, Gallade fails to do a lot due its middling Physical bulk and average speed, only coming in on some resisted hits (although its resistances are Physically based, so it takes a ton even from them, for example, about ~50% from LO Chan's Drain Punch) to fire off hits. Versus stall, while it can do something, Quagsire and Pyukumuku both check it quite consistenly (ok there is a chance they get 2hkoed, but its not that big and they can Toxic it and recover stall), aswell as bulky Ghost types like Colbur Gourgeist-XL/Palossand, Sableye and bulky psychics like the aforementioned Musharna (we must remember that, while most people, me included, want it gone, its still here so we have to take it into account), bulky Beheeyem, etc. As I said, Balance is the playstyle it threatens the most, but even then they have checks such as all the ones I have mentioned for stall (and no, they're not solely used for checking Gallade) and more such as Colbur Harvest Exeggutor, Oricorio-Sensu, Haunter, AcroZard, etc (yes, those are mostly offensive checks but you don't need to have a hard stop on every team so that we can tell its not broken). Overall, I don't think this is neither as bad as people pretend it is and its manageable.
This one might be a bit more controversial. This might be more personal experience but I feel like people underprepare for this thing, barely having Scarfers or strong priority (if they do, at all), and its a big reason to why people want it gone. Vivillon is super predictable, since pretty much 3/4 of its moves are always the same. While it is easy to support, we must not forget it wants hazard out of its field but also on the opponent's field, and while it has good synergy with most hazard removers, keeping the hazard game at your favour can prove to be quite difficult sometimes. Its rock weakness also means its not splashable, which is definitely a huge factor. The base 89 speed put it right below anothe premier QD Sweeper in Lilligant, and because of it, most scarfers rn are base 91+ to revenge it and the get the bonus on Vivillon. Offense gets troubled quite a bit for it but it isn't impossible to deal with, due priority mons like Kangaskhan, Piloswine and Lycanroc, revenge killers like Kadabra, Chatot, Oricorios and Pyroar and even some defensive answers like Assault Vest Lanturn, Klinklang, etc. The whole offensive pressure sometimes also makes it difficult for Vivillon to set up, and it often faces 50/50s when it has either to boost or put something to sleep. While it is true that these can be chipped, you need to play carefully not only around it, since other speed boosting sweepers also have quite the same matchup. Just like Gallade, this is a fearsome balance breaker, but again you have the same checks and even more defensive answers. The metagame has some checks to it but people hasn't adapted and want it gone. Don't ban it, at least not yet.
I don't have much to say about this one. Its a super bulky wincon that can set up versus common attackers. I feel like people are mindlessly spamming Offense with fast not-so-powerful attackers and that's why they see Mush as such a pain. Musharna is not impossible to check defensively with Steel-types and things like Skuntank around. Its similar to Duosion, except its bulkier, can tank Knock Offs and its way more vulnerable to status. While the Fairium Z set has been hyped, it makes Musharna almost dead-weight through the battle since it really needs Leftovers to pivot around mid-game before it sets up (since Moonlight has few pp, it has to save it for when it boosts). You guys need to start using stronger wallbreakers so they can actually pressure it. While I don't think its healthy, we shouldn't just quickban it. Maybe a suspect test in a near future, but imo the meta is still too new to take such drastic decisions.
Okay. I think people overstimate this thing's potential. A lot. While I can't deny Gallade is a fearsome wallbreaker, its far from perfect and its not really unhealthy or broken, neither restricts teambuilding. For starters, Psychic-, Ghost- and Flying-types are pretty much a must in a meta with so many threatening Fighting types. The playstyle Gallade truly shines against is balance, since it gets more opportunities to switch in and do its job as a breaker. Versus more Offensive playstyles, Gallade fails to do a lot due its middling Physical bulk and average speed, only coming in on some resisted hits (although its resistances are Physically based, so it takes a ton even from them, for example, about ~50% from LO Chan's Drain Punch) to fire off hits. Versus stall, while it can do something, Quagsire and Pyukumuku both check it quite consistenly (ok there is a chance they get 2hkoed, but its not that big and they can Toxic it and recover stall), aswell as bulky Ghost types like Colbur Gourgeist-XL/Palossand, Sableye and bulky psychics like the aforementioned Musharna (we must remember that, while most people, me included, want it gone, its still here so we have to take it into account), bulky Beheeyem, etc. As I said, Balance is the playstyle it threatens the most, but even then they have checks such as all the ones I have mentioned for stall (and no, they're not solely used for checking Gallade) and more such as Colbur Harvest Exeggutor, Oricorio-Sensu, Haunter, AcroZard, etc (yes, those are mostly offensive checks but you don't need to have a hard stop on every team so that we can tell its not broken). Overall, I don't think this is neither as bad as people pretend it is and its manageable.
This one might be a bit more controversial. This might be more personal experience but I feel like people underprepare for this thing, barely having Scarfers or strong priority (if they do, at all), and its a big reason to why people want it gone. Vivillon is super predictable, since pretty much 3/4 of its moves are always the same. While it is easy to support, we must not forget it wants hazard out of its field but also on the opponent's field, and while it has good synergy with most hazard removers, keeping the hazard game at your favour can prove to be quite difficult sometimes. Its rock weakness also means its not splashable, which is definitely a huge factor. The base 89 speed put it right below anothe premier QD Sweeper in Lilligant, and because of it, most scarfers rn are base 91+ to revenge it and the get the bonus on Vivillon. Offense gets troubled quite a bit for it but it isn't impossible to deal with, due priority mons like Kangaskhan, Piloswine and Lycanroc, revenge killers like Kadabra, Chatot, Oricorios and Pyroar and even some defensive answers like Assault Vest Lanturn, Klinklang, etc. The whole offensive pressure sometimes also makes it difficult for Vivillon to set up, and it often faces 50/50s when it has either to boost or put something to sleep. While it is true that these can be chipped, you need to play carefully not only around it, since other speed boosting sweepers also have quite the same matchup. Just like Gallade, this is a fearsome balance breaker, but again you have the same checks and even more defensive answers. The metagame has some checks to it but people hasn't adapted and want it gone. Don't ban it, at least not yet.
I don't have much to say about this one. Its a super bulky wincon that can set up versus common attackers. I feel like people are mindlessly spamming Offense with fast not-so-powerful attackers and that's why they see Mush as such a pain. Musharna is not impossible to check defensively with Steel-types and things like Skuntank around. Its similar to Duosion, except its bulkier, can tank Knock Offs and its way more vulnerable to status. While the Fairium Z set has been hyped, it makes Musharna almost dead-weight through the battle since it really needs Leftovers to pivot around mid-game before it sets up (since Moonlight has few pp, it has to save it for when it boosts). You guys need to start using stronger wallbreakers so they can actually pressure it. While I don't think its healthy, we shouldn't just quickban it. Maybe a suspect test in a near future, but imo the meta is still too new to take such drastic decisions.