Gotta say I have no love for the big leftist subs but that's a pretty cheap shot.
Their choosing to purchase luxuries, in a world where luxuries must be paid for in a system they didn't design, choose or want to live under, doesn't negate that they are opposed to capitalism.
If you want to argue that they're possibly a bit too sanguine about the prospect of their favourite luxuries existing under communism or whatever, fair enough. But that's a separate argument from whether they're stupid to pay money for stuff that makes them happy.
Can you give any reasonable by means in which they could do this and succeed?
So much of this stuff just sounds like infeasible conspiracy theories. If, hypothetically, Meta did do such a thing (somehow, still not clear how or frankly why?) all that it would mean is that anyone who disagreed could defederate from Meta, or would be defederated from Meta... which given half the servers in existence seem to want to defed them up front anyway, doesn't seem to make any odds.
It's all just very confusing hearing about these lurid ideas for things Meta could do with the fediverse that simply don't make a lick of sense either in terms of motivation or implementation.