There's one more benefit.
In a federation, you can join the new less shitty version, AND stay in the old one going downhill.
You can vote for the new thing, without giving up on the old. You simply switch which one you post to.
Imagine if you could have Reddit and Lemmy, in the same app, seamlessly intermingling, but actively reduce how much you contribute to reddit, while actively increasing how much you contribute to lemmy.
You could contribute to that change and improvement, with ZERO trade-offs. How many more people would support the next thing, if they could adopt the new without discarding the old?