Federated platforms can still be censored and walled off. Not all Mastodon instances are peers, and your data isn't portable. It still has most of the same pitfalls as the platforms we complain about today.
P2P is naturally efficient. The best ideas will gain traction within their memetic networks, and you can branch out and explore anything and respond to it.
Sign and publish with a pubkey so you have pseudonymous identity and can keep track of peers. Publish and consume through a gateway proxy or VPN if you want to keep your IP private.
Supernodes can help with scaling, especially for mobile clients.
You can block whomever you dislike or share only with your direct network. You can write your own prioritization algorithm to cut down on noise and create high signal channels. You can archive whatever you like easily.
It should have been P2P all along.