>For people who own domains, this is easy: they just point the DNS records at their host and tell their host that their identity should be served from their domain.
I think @h is working on this. I don't know all details but one part of the solution is documented here: https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-612d.md
>using DIDs as AP identifiers
This is not necessary, we can add DIDs in a backwards compatible way: https://codeberg.org/fediverse/fep/src/branch/main/feps/fep-c390.md.
>“Doesn’t this just move the centralization point from identity resolver to the DID resolver?”
Resolver can be self-hosted or be a node in P2P network. Some DIDs don't even need resolvers, for example did:key