Nostr is already designed to have some degree of centralization, that's the only reason why it has a chance of working, unlike fully p2p systems.
Discussion
Why don’t p2p systems work?
The internet is too big.
The internet will eventually be too big for any topology. The only solution is design it to limit data transmission around real-world lines of contact. Universal reach is impossible, but you can get close via degrees of separation. Only takes 3-4 hops to reach most of the world currently.