Having LLVM doesn't mean that webassembly Just Works, in the same way that having LLVM doesn't mean that all of its architectures Just Work. And even after getting past the "hello world" stage, there's a lot of other work to do to make it more than just a toy.

Let's take Ada, for example. https://blog.adacore.com/use-of-gnat-llvm-to-translate-ada-a... talks about how to use Ada to build stuff for wasm, but you need to include https://github.com/godunko/adawebpack/ to make things work well. Someone had to write that code.