This is no longer true, there's various high level types that WebAssembly can pass around, such as reference types (opaque objects from the outside world, i.e.

This is no longer true, there's various high level types that WebAssembly can pass around, such as reference types (opaque objects from the outside world, i.e. JavaScript objects) and all the new GC types. So the only thing stopping you from calling into web APIs is importing them into the WebAssembly, which atm is indeed still a manual process (or automated with some codegen).