The memory and execution model for higher level work needs to not have async. Go is the canonical example of it done well from the user standpoint IMO.
Actually, I was and am primarily a Dart developer, not a JS developer. But function color is a problem in any language that uses that style of asynchrony: JS, Dart, etc.
However, gevent has to do its magic by monkeypatching. Wanting to avoid that, IIRC, was a significant reason why the async/await syntax and the underlying runtime implementation was developed for Python.
Another significant reason, of course, was wanting to make async functions look more like sync functions, instead of having to be written very differently from the ground up. Unfortunately, requiring the "async" keyword for any async function seriously detracted from that goal.
To me, async functions should have worked like generator functions: when generators were introduced into Python, you didn't have to write "gen def" or something like it instead of just "def" to declare one. If the function had the "yield" keyword in it, it was a generator. Similarly, if a function has the "await" keyword in it, it should just automatically be an async function, without having to use "async def" to declare it.
Similarly, a function that calls an async function wouldn't itself be async unless it also had the await keyword. But of course the usual way of calling an async function would be to await it. And calling it without awaiting it wouldn't return a value, just as with a generator; calling a generator function without yielding from it returns a generator object, and calling an async function without awaiting it would return a future object. You could then await the future later, or pass it to some other function that awaited it.