Why is Server Content Federated Instead of Identities w/ Metadata?

Hello fellow fediverse feds, I'm 100% sure this has definitely been thought of before, but I'm apparently bad at googling the idea, so what's up with this?

There's obvious problems with the federation model:

• It's a moderation nightmare and standards are effectively that of the worst website Federated with
• It's a bandwidth catastrophe, last I heard Lemmy broadcasts every single vote to every Federated server??? At serious scale this is a genuine waste of resources with real carbon cost. I've read mitigations to this that seem to basically be going down the same route of Usenet or cryptocurrencies, such as having trusted servers/shards/whatever bundle transactions, which is a whole new mess
• No cross-server identity management (not an inherent problem though). Super important ™️ clout chasers can try to squat their names on the big sites, but nobody's stopping anyone from doing a "REAL Elon Musk crypto give away" on a new server with the name not taken yet.

So what if users just had an rss-like experience of subscribing to individual communities on any server they pick? Their signed identity could carry meta data to facilitate cross-server connections (DMs go to XXX, also member of X, Y, Z, etc), and servers would only have to worry about serving and moderating their own content. What's lost? Discoverability? That seems lower stakes to centralize than moderation and corporate control.

Obviously the technology already exists: we have centralized OAuth providers and a more decentralized regime could be built off asymmetric encryption, but the attempt to apply it here is where?