WebAssembly does not cover use cases that require a ton of C#<->JS interop, and it may never adequately cover it. You end up needing a very complex interop bridge similar to C<->JS interop. A solution like Bridge can compile to JS, making interop near-zero-cost.

Thanks for fantastic answer to my concern (for those who might object that kevingadd didn’t cite his sources, given his background he pretty much -is- a primary source)