You are right that all software needs to update to take advantage, but that doesn't mean you can't make it incremental... For example Pkarr TLS certificates don't work in browser, so any Pkarr based server needs to also have an endpoint accessible by ICANN and their certificates... But that is already the baseline for Nostr relays... So now you only need to add an endpoint using Pkarr TLS and clients capable of understanding that uses that, in they very unlikely chance of being censored at DNS level..
The main problem is that there are no users anyways so despite all that being possible already a year ago, no one gives a shit ... And both wisdom and happiness is to smile while saying that :) 😊