At least when I used it ~2 years ago: an extremely complex type system with a huge learning curve (unless you're going to just write Java in Scala), poor documentation, and a very slow compiler. That's to say nothing of the JVM-based runtime.
Scala’s implicits, mutable/immutable collection bifurcation, infix/dot syntax interchangeability for method invocations, tendency of libraries to implement their own mini language, ...
the JVM is an incredibly heavyweight runtime compared to CPython. I don't think we're going to find the next beginner-friendly language coming out of the most professional runtime in human history.
True, but I don't think that is what the OP was taking about. The language itself is rather independent of the runtime. Scala compiles to native code or Javascript as well.
The JVM is definitely memory hungry (excluding cherry-picked examples such as 'set top deployments' or the Java Ring from the 90s), moreso than any other language runtime referenced in this discussion.
