Except even the stuff that could be replaced is just using it a Twitter alternative. Fountain could be a pure nostr app, host mp3s on relays, change the data structure and host the metadata on relays instead of RSS feeds, but it chooses to engage with the Twitter alternative and be a 'nostr' app.

Wavlake could do the same thing for music.

Even the apps that claim to be 'doing things different' are just using legacy protocols and tacking on the nostr Twitter feature.