The federation aspect adds complexity. A lot of complexity.
The only thing the fediverse might enable is nobodies like me can theoretically write social media software and actually get them successful without becoming a VC funded social media startup and have to resort to ads and premium tiers.
But things that couldn't be done without the fediverse as a base? Nah not really.
Note that the concept of federation is really old. Emails are a form of federation. XMPP was federated too. Heck, Diaspora* is pretty old and tried to make open Facebook for almost as long as Facebook's been mainstream.