I believe the difference is that it's more about fetching blocks and less which bitcoin nodes you connect to.

If I run a new bitcoin node, I can be pretty sure that my node have the same view (shared reality) as everyone else on the bitcoin network. Thanks to PoW, my node can just follow the chain with the most PoW in it as long as my node "randomly enough" connect to nodes.

On nostr, to which relays I connect to is important to have "shared realities" with others, no? I can't just randomly connect to relays and think my view is the same as everyone else on nostr, no?

So I think OP is more concerned about censorship resistance than centralization since yes, Bitcoin Core includes DNS seeds.