> A stackful coroutine framework would probably have allowed for the same without requiring WASM

Interestingly Rust actually had this built in originally, but it was taken out of the language since it could be added back in as a library, and the devs thought it was important that Rust did not hide any costs from the user.

Which I can certainly buy. Especially once you consider use cases like embedded development. That said, it'd also suuuuure be nice to be able to opt-in to something like that and avoid the async headache.