But this cannot made work generically in the current ecosystem, as there are no common abstractions here. We can't come up with those unless we have buy-in from other players.

For applications, that doesn't really matter: you pick one Listener type and you're done. Applications aren't very generic.

For libraries, that's harder, but there's strategies around that make it feasible to work with this situation (mainly: injecting the exact type to use into your library).

Finally: there's a flag in async-std called "runtime". If you turn it off, you can use async-std without that behaviour, at the cost of having to bring your own runtime.