So because there are lots of them they can form their own groups. The breadth of player ability in the group of people that are theoretically(stressed because it is not a certainty) being considered off meta is going to be much more broad.
Because it will? Any guild looking to progress mythic seriously will have these requirements and I have been in several Heroic guilds who also want an easier time killing bosses, so the expectations will always be there.
Just because “you’d hate to be in such a guild” doesn’t mean that lots of them don’t exist. It’s not all just pugging.
The majority of people that play WoW are not in cutting edge mythic raiding guilds, and it’s about time the game stopped catering entirely to them. They will have options to do what they need to do.
Which will result in a larger group of people (from a wider demographic of players) rejected as being off meta (something you have already said you think will happen). But you think this relatively large group of people won’t just form their own groups? I don’t think that seems likely.