using a centralized registry web service is a cop-out, but there's not really an obvious solution either

DHT and blockchain are basically the opposite extremes in this case, blockchain can provide a bad user experience because it can never forget (no way to delete private information), DHT can provide a bad user experience because it's potentially lossy (same frustrations as say, IPFS)

nostr takes the "roll with the chaos" approach by not having any kind of guaranteed global identifiers, which is, another kind of compromise 

 True, but the lossiness can be overcome by relay services, similar to nostr relays. Should be pretty cheap to run and ideally just built into whatever other servers you publish things to anyway.