I raided mythic all of BfA until the guild fell apart mid Nyalotha
Killed all but G'huun in Uldir
We got CE in BfD
Killed up to Zaquul in EP
The guilds that are benching people for not having multiple specs playable or requiring multiple toons are actually less that 1% of the player base and almost 100% of them are calling the the covenant system and soulbind system to be changed to allow switching between the player power.
This comment also ignores the fact that I was talking about farm content IE. bosses you've already killed. No one is getting benched in High End guilds on farm content. Farm content is literally where you bring your bench in to get experience and gear. On progression yes if you aren't pulling your weight you will get benched. but on progression in a mythic guild you should be perfectly willing to be using the optimal setup for that fight that's what you signed up for.
I'll ask you the same question you asked me about playing at a high level. My logs are all public I'm the only character in the game with my name they are easy to find