React was never intended to solve browser inconsistencies. Of course it developed hand-in-hand with the tools that solved those (transpilers, polyfills, bundlers), but that was not the main reason it was invented or became popular.
The original motivation was to describe UI as a function of state. It sounds trivial, because it is when server rendering, but once you start sprinkling enough interactivity it can get messy. It's of course not the solution to everything, but above a certain level of complexity I really think you should let someone else handle the problem of syncing state with UI, and JS on its own will never do that for you.
Yes that’s a good point sorry I just gave one e.g. from the article of IE event handling.
Re the original purpose of react being syncing state, I’m really not sure this small problem is actually worth the trade-offs of massive complexity and lock-in, nor that react is a good solution for it (double renders, persistent rendering bugs, use state, hooks etc).
It’s not something important to lots of apps and there are loads of other options from simple polling to web sockets to reloads, this can be done in a far simpler way without react. Also the use cases where this is central are really quite small.
The original motivation was to describe UI as a function of state. It sounds trivial, because it is when server rendering, but once you start sprinkling enough interactivity it can get messy. It's of course not the solution to everything, but above a certain level of complexity I really think you should let someone else handle the problem of syncing state with UI, and JS on its own will never do that for you.