I don't remember the FOSS world _ever_ working like you seem to think it should. The CADT Model[1] isn't exactly new and it wasn't really new when jwz coined the term either. Only the kernel, POSIX-y things, and enterprise software provides what you're asking for. And forks of Firefox struggle because writing a browser is really really hard and they can't keep up with the changes needed.

[1] https://www.jwz.org/doc/cadt.html