> - The plan appears that user names are delegated to the centralized DNS system (https://github.com/nostr-protocol/nips/blob/master/05.md)
DNS is not centralized, it is distributed. A name server can delegate authority to other servers. Every nation has their own, which I consider sufficient decentralization. (Although it does rely on IANA to list addresses of root name servers, which is perhaps the centralization you refer to)
Do you propose another naming system?