Nostr is a useful contrast, though it sidesteps more than it solves: relays are intentionally dumb and replaceable stores, identity lives entirely in the keys, and the payloads are small. A dead relay is just a reconnect. That model breaks the moment the interesting payloads get large, at which point you need exactly the durability and seeding incentives Dat never quite cracked. So 'relay mesh + keys' is a great answer for small messages and a non-answer for files.

The persistent complaint about NAT traversal is also worth taking seriously: anything that requires a public reachable peer as a rendezvous point tends to end up depending on a central service, which is why these ecosystems keep re-centralizing around bootstrap nodes.