That's kind of my point. You end up with the option of 1) it's centralized. Everyone only cares about who Mastodon.social federates with. How it's built to work doesn't actually matter. 2) It's centralized. Users wrestle control from Mastodon.social and everyone cares about who some other server federates with. 3) It's a balkanized mess. You spend all your time worrying about who you're federated with so that your content and the content you want to see become accessible. 4) It's decentralized, but nobody really bothers with banning anyone anyway, because it leads to the other scenarios and they are worse.