>you can write it in a tight, minimal way that doesn't bloat the page or slow it down.

Yet most people don't.

There are some problems with the language itself but it's mostly from a users perspective that I find it frustrating.

Of course you can, but most people still opt to pull in a whole framework (React) or heavy library (jQuery) just to achieve what's essentially a few XMLHttpRequests and some DOM changes.

Maybe because it is easier to track one library, react and jsx. I wouldn't use xmlhttprequest since the request api exist.