Have you never heard of Mastodon?
I've *heard* of it. Why?
It existed for a long time. Over 1 million users Somewhat-decentralized Better user experience than Nostr by far Better backend and frontend tech Try https://poster.place to see sample
Mastodon isn't it. It has a bunch of inherent problems that can't be rectified. The fact that you are attached to one server for instance. It recreates the problems of email in social media.