There’s no real / true decentralization

That’s not exactly true.

That said, you do need some form of centralized service to connect peers, but you can federate those. It’s only job would be to connect peers, and a STUN server w/ TURN fallback is usually the approach here. These instances don’t need to store any data long term, they just need to connect peers, and the client is free to choose any instance they want, or host their own.

That’s how Tor works (entry nodes), and most decentralized systems use a similar system.

One of the best parts here is that offline often just works, and you can sneakernet around firewalls (e.g. if you visit China or something), and all you need to do is connect to a local relay to find local peers.

Blockchain

My understanding is it’s only used for name resolution, so the number of data points here should be in the thousands, not millions or billions, so the resource usage should be minimal.

Basically, the blockchain is functioning as DNS here.