It seems to me like you don't understand the crucial difference between Twitter and Mastodon.

There's no such thing as Mastodon, a singular social network. Mastodon is a series of instances that talk to each other. A sysadmin running the instance can do whatever he pleases in his instance, including closing the registration, banning entire instances from communicating with his instance, and enforcing whichever rules he wants to enforce.

Mastodon doesn't deal with such issues at all. It's sysadmins running Mastodon instances that are supposed to deal with such issues.

It's more like reddit, where mods of subreddits have nearly complete authority over their own space on the social network, than it is like Twitter, in which a single entity is in charge.