Yeah there are a number of successful compilers from functional languages to Wasm. It's definitely doable. I just wanted a backend that was more focused on being a portable target for functional languages. Throughout these comments I list a number of issues I take with Wasm. It's cool and I want a SaberVM->Wasm transpiler soon but the Wasm spec definitely doesn't look like something I want to be tied to in the long run.

To answer your question more specifically, I've heard from a number of people that the structured control flow of Wasm is pretty painful to deal with when writing a compiler. Doing a relooper pass over a CPS or even SSA IR should not be a necessary step. I get the sense that many compromises are made for Wasm to work.