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.

[0] https://fediverse.party/

[1] https://writefreely.org/

[2] https://fediverse.party/en/pixelfed/