I'd like less focus on the network and more on individual servers, with their own names, policies, and reputations. Then users aren't thinking about whether to join one huge network - they're thinking about whether that server is the kind of place they want to be. (https://wandering.shop is a good example of an instance that is explicitly going for certain vibes.)
It would allow individual pre-existing communities to create their own spaces, ones which would prioritize those communities' experiences and needs over their connection to the rest of the fediverse. I'm imagining something like Dreamwidth or Fur Affinity or the many old-fashioned forums out there, just with the ability to follow users or navigate to topics on other instances if you know their names or URLs. I'm really not worried about discoverability outside the instance - to me, the instance is the platform, and anything outside of it is just an additional thing I can get to if I want it.
That being said, I think this approach is probably incompatible with trying to create a general-purpose social media site that also attracts a large number of users, at least not without a hefty marketing budget.