Rewrites are hard and costly, which is rarely taken into account. Even just maintaining a competent fork is hard enough.
I think it's probably worth the effort, but I'm not quite sure how you get from A to B without just having some super competent eccentric multi-billionaire finance a series of massive development projects.
And Elon Musk is busy doing rockets and electric cars!
Few have attempted a reboot, yet the zeitgeist is definitely there: ZFS, Wayland, Metal, A7, even TempleOS (or whatever its name is these days). Folks are starting to say themselves 'hey, we built things, we learned a ton, we do feel the result, while useful, is a mess but we now genuinely understand we need to start afresh and how'. It's as if everyone were using LISP on x86 and suddenly realised they might as well use LISP machines.
I too fear we just loop over, yet my hope is that in doing that looping, our field iteratively improves.
Very hard to avoid the 'now you have two problems' trap.