You do not speak for me. I want decentralization, self hosting, and the right to repair. The modern technology ecosystem has failed me in every one of these areas.
That's kind of the point, IMHO.
Mastodon doesn't speak for decentralization, it is decentralized. And that's not really splitting hairs here, it's an important distinction.
I could set up a Mastodon instance (although Writefreely[1] and Pixelfed[2] are more my speed) that advocated for centralized everything. I could even ban folks who argue for decentralization and delete any comments they make in favor of same.
It's a tool that allows folks to speak for themselves, without a central corporate authority dictating what's acceptable and what isn't.
If you don't like a particular Fediverse[0] instance, move to another one or set one up for yourself.
Twitter still exists and is still functional, so why would absolutely everyone move over? I don't think that's ever happened. Every system I've seen where people migrated over elsewhere had it happen over a long period of time.