Alright so I want to discuss the ability of stallbreaking Megas in this meta (no Aegi)
In the past stall could not cover everything and it can't now. You pick and chose what you're weak to, to assure that you have the best chance in the vast majority of matchups by accounting for metagame-relevant threats. stall teams can run Gliscor/Lando-T/Clefable for Mega Heracross, Slowbro/Mew/Cresselia for Mega Medicham, and Mega Gard is a tough one but can ultimately be dealt with because it doesn't really have that many switch-in opportunities/can be worn down, and there are options to check/counter it for sure. Most modern stall teams don't run Aegislash for these threats, and 2/3 beat Aegislash anyways, but that's not the point -- the point is that Aegislash limits the presence of these threats. Since stall can prepare to beat these threats, even though they are an issue, I don't think it's a problem when you consider that these Pokemon are basically dedicated stallbreakers. This meta is also perhaps not so representative of the long run. These Pokemon still have their other issue, a poorer matchup vs offensive teams than Mega Gyara/Charizard X/even Mawile. For this reason those Megas will continue to thrive, but a few of the stallbreaking Megas might get the spotlight which can be dealt with by stall and add diversity to the metagame. If we absolutely HAVE to make more bans, then so be it, but this is being blown way way out of proportion. I am biased towards stall/bulkier builds, and I still feel that stall is good in this meta. In fact the increased prominence of these threats and loss of Aegi to account for actually gives me more room to account for specialized breakers like these because I don't have this versatile annoying as fuck threat to deal with too.
I'm assuming the team papai noel is talking about is this one: Mega Venusaur / Gliscor / Chansey / Slowbro / Skarmory / Quagsire. This is the perfect example of picking and choosing what you're weak to, and the ability to wear down/get around certain stallbreakers. Gliscor for Mega Hera and Slowbro for Mega Medicham. Gliscor can deal large damage to Mega Gard with EQ and hit it with Toxic post-Mega. Mega Venusaur can survive a Psyshock well enough and hit it with Sludge Bomb. Slowbro can Toxic it. Quagsire can Toxic/EQ it. Chansey can wear at it with SToss and status. Obviously these are not 1v1 scenarios with Taunt Gard but Gard has to get in somehow. This is also all a stretch, and a well-played Mega Gard is running it over, but it's not like the team doesn't have a chance.
A stall team that's been used in WCOP is Charizard X / Alomomola / Clefable / Skarmory / Amoonguss / Gliscor. This team eats up Mega Hera with Glisc and Clefable. It's weak to Mega Gard and Megacham. It can bait certain moves and play around Megacham to some extent, like it has to Ice Punch Gliscor, Zen Headbutt Clefable, and HJK Skarmory, plus Alomomola has Scald Toxic and Protect to play around it, and Zard X can burn it. Mega Gard is really difficult with this build, even more so than the last one, but again, you can't cover everything.
So stall pick and chooses what it's weak to, as I've said. The only thing I can say is difficult to prepare for adequately is Mega Gard, though even that depends on set, because if it's anything but Taunt you can do the job with Chansey no problems. Stall can wear away at Taunt Gard with attacks, and there's a thing called Mega Scizor that beats it, so it's not impossible.
The point I'm making with this post is not that these stall teams are realistically beating all of these stallbreakers that any calls that banning Aegislash 'makes stall impossible' because these stallbreaking Megas will become more common is untrue, due to two reasons: it's reasonable to assume that these Pokemon will gain viability, but not become THAT much more common, and stall has options to cover them such as to minimize its weaknesses. And if we HAVE to make more bans, we can, but I doubt it will be necessary.
Also instead of engaging in petty discussion argue Aldaron's points, or the anti-ban side is not providing their end and arguing useless details.