I’m not sure I agree. For example, nothing about Erlang makes it unsuitable for a browser environment, it can handle running single threaded, or distributed across workers, where each worker runs its own scheduler. The only limitation is interacting with the DOM, since that must all happen in the main thread, but it is still possible to treat that the same way other blocking I/O is dealt with in the scheduler.

I’m actually working on a compiler/runtime for Erlang for WebAssembly, so I’m maybe more familiar than most with how it works in practice.