WASM also can't "run in any environment" since it relies on imports, and different environments will have different things available to import. The only way around that is by only defining very minimal behaviour... like it does on the web. But then you can't do anything useful with it by itself.
I think we say 'run in any environment' when what we mean is 'recreate the environment on any machine'. And this is often more of a continuum than a black and white answer. I can get a lot of things done without low level access to the GPU, or printer, but I can't do everything.
