I think the combination of "well-known" public relay list (kind:10002) directories like purplepag.es + nip05 hints + relay hints in events whenever someone is mentioned in a Nostr event + nprofile/nevent relay hints are enough to allow any client find out where any other public key is publishing to. The world is not so big after all and even on the internet no real person is capable of consuming content from more than a few thousand others at best.
If Nuh 🔻 (npub1jvx…7yqz) wants to call this a kind of DHT that sucks so be it, to me it makes more sense because it is more flexible and fluid, can be implemented in parts and incrementally, and in the best-case scenario (the one in which you get the relay address from an immediate hint, for example) it is more efficient than any DHT.
I am also not against having a Nostr DHT for this either, as I told him a million times. But the DHT would necessarily be just another method to help in the task of finding a relay list.