> In some sense of the word they are already shut down.

C'mon. Let's call a spade as spade: you wanted to complain about moderation and you shoehorned it into conversation. In no way does it make Twitter "shut down".

Neither does any point on the Fediverse. As long as operators think they can run their site any way they want instead of obeying a common protocol then they're federated in name only. To put it another way: If I can never trust that my email will make it to someone on gmail due to the opaqueness of their spam filters, with no way to be whitelisted by a recipient, then email has been thoroughly decommoditized and centralized... and so too a 'federated' system where operators set arbitrary rules that result in whatever server they don't like being unreachable.