I have touched both and async in Rust is indeed half baked at the moment. That a factor of immaturity of Rust and maturity of Scala. I also had a Scala codebase that had 4 different Future classes, due to it having been an early adopter.
I was thinking if the language itself, where it needs to keep backwards compatibility with Java (the distinction between case classes and classes, for example) and over engineering (implicit action at a distance all over the place). I think Scala is a nice language buried in way too much syntactic sugar. Interestingly enough, Rust's syntax doesn't bother me but quite a few people seem out off by it.
Rust is new and it advances slowly but at a steady state. Given its immaturity in some areas I can only go off potential and the async story seems to have a bright future, despite it's somewhat underwhelming present.
The async situation for Rust is very much in flux, of course - see https://areweasyncyet.rs/ for details and updates. It's definitely a pain point at this time, and stability itself is an important value so I can see this making Rust less desirable for some - but calling it a "trainwreck" that the Rust community is supposedly to blame for just seems pointless, other than as snarky flamebait. That sort of comment is a good fit for `rustjerk`, not for the sort of substantive discussion we seek on HN.
Rust is a nice language for threaded programming, but the async situation is a trainwreck 4 years in the making.