Still reading and hearing takes that Mastodon has “failed” as a Twitter alternative. Listen, it’s ok if it doesn’t work for someone—unlike Twitter, I think Mastodon requires more effort and cultivation to produce an experience that feels meaningful. It’s been worth it for me. But there is definitely a smell of…not sour grapes but people making broad assumptions based on their own experience while ignoring millions of other people. Will Mastodon top 100 million? Who knows. Who cares?
The fediverse is a concept more like the original internet -- a bunch of little pieces that connect together independently without some broader authority exercising power over it.
Short-sighted people would prefer there be an overarching authority because they imagine that they themselves would be in charge of that overarching authority. Whatever you think of Elon Musk, his takeover of Twitter is a perfect example of the fact that power changes hands, and some people will like the new powers, and other people won't, but it doesn't matter whether you like them or not they will be the ones with their boot on your neck.
By contrast, a distributed system like the fediverse lacks and overarching power to implement policies that you would like, but also lacks and overarching power to implement policies that you don't like. Instead, individual operators get to choose how they want to run things in their little domain.