I don’t think the comparison to react makes a ton of sense - Facebook created react as an open source project, but once you download react, you have a copy of it for yourself and you don’t need to check in with Facebook any further. They don’t own your react app or its data.

I may be misunderstanding, but it sounds like threads will not be like that: they will be using an open standard that they did not create for a social network that will track you and gather your data every time you use it.

(I am for defederation)

Tbh I think a lot of developers either don’t know that they need to fix this or don’t know how to fix this. They get a mock-up from the designer and implement what they see, and their implementation work is reviewed be other engineers and product people, but less often (IME) by UX. Sometimes there’s no one to push for fixing these kind of things, especially when the developers don’t use the software they make in their own day-to-day lives.