[AuthAuth]

I disagree because you dont just want "twitter for MMA" you want the whole network. So you want to be a good citizen and have instances federate with you. But most wont because of the nature of the content. So users would prefer platforms where they can follow all content from a single account.

[wizzwizz4]

You can still have those instances federated with you. Consider the various language communities on the Fediverse: there's little overlap between them, except where speakers are bilingual, but their instances do federate. You can do the same thing with interests.

There is no advantage to centralised systems in this regard: they have all the same problems.