You are possibly right, but it would be sad if we our choices for writing programs with a UI are: write in javascript or compile to javascript. There are many languages out there, webASM would allow them to work without the massive pain of cross-compilation.
I guess I am just an idealist screaming about how packet switched networks are unreliable and we should all use circuit switched networks.
If you want to use a different language, why would you care about the compile target?
Compiling is done by the compiler. So to the developer it is the same. No matter if it comiles to Javascript or Webassembly.
In the end, I don't think writing code for the web in languages other then Javascript will take off. Simply because Javascript will always evolve to fit this specific environment. And therefore will always be the best choice. While other languages will evolve to be the best fit for their niche.
Cross compilation always comes at a performance cost. Moreover, it is another compilation target your compiler needs to support. When that compilation target is a high-level language, supporting it is harder. This means java-script as a compilation target is less likely to be added.
The use case for wasm is basically doing cpu/memory intencive work in a worker process. In order to use wasm for UI you need lots of glue and ducttape, and the end result will be something using 2d canvas.
I guess I am just an idealist screaming about how packet switched networks are unreliable and we should all use circuit switched networks.