I agree with the sentiment, but I'd say specifically the Fediverse is the only real place for a truly decentralised option.

It doesn't need to be Mastodon. You don't need to be on Mastodon to interact with the Fediverse or be part of it, and that is the key strength. Mastodon can be corrupted and the Fediverse is still there.

That could include Bluesky over time - you can follow my Mastodon from Bluesky via a bridge [1] - any desirable parts of their protocol, will be copied or emulated or bolted on the side for other Fediverse projects.

[1] https://brid.gy/