It's an open question whether React succeeded because of technical advantages or because of Facebook's initial support and the job market creating its own dynamic (people go where the jobs are).
> React is a library that should have been a framework.
React is a library that powers several different frameworks, as well as lets people use it without those frameworks. If one size fits all, answer-for-everything frameworks were the optimal solution for all problems, Angular would own the world and we wouldn't need React.
> React really isn't the thing people have decided is the optimal solution
My point is there is no one thing people have decided is the optimal solution. React is an element of snow me of (several different) things people have found is optimal for some problems, and not part of others.
> jsx and keeping presentation tightly coupled to business logic is.
JSX is more generally than React is, which is why many not-React solutions use React, too, though even that is far from universal. Tight coupling between business logic and presentation is, OTOH, far less generally what people have decided is optimal.
I've seen entire apps written as React components/hooks, the whole thing, no redux/mobx/etc managing state above the level of necessary local UI state. React markets itself as just a library but the truth is people tend to go all in precisely because there's too much pressure to research a whole stack for yourself.
Literally everyone has to cobble some n-factor framework together and given the amount of inexperience out there, what results is a damn nightmare.
React solving the state problem natively would have made it an industry game changer. What we have is an industry mess.