I sincerely believe this is Rust's ballpark; hell they even started the project with that idea in mind.

The problem with custom stacks is you essentially need to have a custom runtime and it makes calling into C functions a lot more difficult (cgo isn’t a cakewalk)

This runs counter to Rust’s C++ inherited belief that you don’t pay for what you don’t use and would have have made Rust less feasible for all kinds of other projects.

async/await might not have the best developer ergonomics, but it does have the best implementation ergonomics from a language point of view