Clearly you haven't seen the entire fediverse. There are tons of "free speech" instances along with a garden variety of other "alt" instances that are as active as the mastodon affiliated ones.

They tend to all be mutually blacklisted by each other, meaning that you won't see their posts appear in your federated timeline, however you can still individually follow and interact with accounts across the blacklist line.

What I personally do is host my own Pleroma instance where I can manually configure which instances I chose to associate with. Sure, I don't show up on anyone else's federated timeline but I mostly lurk anyways so I don't care and I get a large degree of control over what kind of content I see.