To me, Scala's issue is identity crisis, not complexity. Some of the community wanted to pretend it is Haskell, and others wanted a better version of Java. But if you want a JVM functional language, why not Clojure? If you want a better Java, why not Kotlin (or update Java). Scala is squeezed by more consistent alternatives on all sides.

I don't think that Rust has the same issue: it has a clear (albeit potentially complex) vision of what it is trying to do, which is distinct from C and more consistent than C++.