There exist a number of self-described free speech extremist instances, and moderated instances that only blacklist spammers like bot servers. There also exist

There exist a number of self-described free speech extremist instances, and moderated instances that only blacklist spammers like bot servers. There also exist instances that will blacklist servers with high levels of hate speech. You can pick or create an instance that meets your wants and needs, but other instances can exercise their freedom of association and choose not to federate with you. Things on the fediverse are also less black-and-white than you're portraying them. Some instances will prevent one instance's posts from showing up in the default public timeline of the whole known network, but will still federate with them; users will still be able to follow or be followed by members of the filtered instance normally. Users on Mastodon can also migrate their account to other Mastodon instances and keep their followers, but migrating from Mastodon to Pleroma is a bit lacking; fortunately, you can still put a redirect on your profile for future followers. TLDR: no, I don't think the fediverse is just like centralized social media.