The component model is what unlocks relatively type-safe interop between modules written in different languages. Given that Wasm is a runtime target for many languages, this is an entirely appropriate and useful goal.

If you have a host system where you want to expose APIs in an language-agnostic way, IDLs are the best way to do that.

You're also conflating the core WebAssembly work with the WASI work. There is some overlap in people, but WASI is developed separately.