I wonder how much of this can be blamed on JS being a relatively gentle and forgiving codegen target.
Anyway, on practice all that means is a bit of lost performance on the DOM interaction. It's a big deal if you do a react-like framework, but the DOM has bad performance anyway, so people tend to not create react-like frameworks.
There is, however, quite a bit you can do in it. TeX has been compiled to wasm[1], it's about 600kb uncompressed 90k compressed (the memory image with latex loaded is about 6MB compressed though - latex is a beast). I think anything computationally intensive would be a good candidate for wasm (it has int64).
Everything was mucked up well into the 2010s with everyone chasing IE compatibility. And not even 3 years later, Chrome had taken over the world. That's a really brief window for anything to happen.
- The places it can run
- The ecosystem it can interop with
Not that it's a bad codegen target otherwise- it's high-level but performant for being so high-level, it's garbage collected, first-class functions, low-level primitives are available for optimizations, etc. But these on their own don't make it super unique
So, yeah, it's a better target than most general purpose languages. It's surprisingly simple to generate, much simpler than to write on. It is also a worse target than most languages specialized on being generated.