> if you choose to forgo a framework, what you're really choosing is to build your own bespoke framework
Bootstrap was written in Less, that needs to be compiled. Is Bootstrap a library?
It's possible to use only the built output of bootstrap as a static CSS file. The nature of react is that your own code is in the other language, so it's fundamentally different than the bootstrap situation.
Correct, it "needs to be compiled to be used in any practical way". That was your criticism of React, and the reason it didn't qualify as a library.
Bootstrap was written in Less, that needs to be built. Is Bootstrap a library?
Any sufficiently complicated framework-free program contains an ad hoc, informally-specified, bug-ridden, slow implementation of half of a framework.