It's not just too complex (we're talking more complex than C++ and Ada) but also poorly designed overall, with so many features that they interact with each other in ways that are pretty much unpredictable.
Odersky himself gave up on scalac and he's writing a compiler and a new language from scratch.
* C++ language specification: 1374 pages (and still includes plenty of "unspecified behavior" / "undefined behavior")
* Java language specification: 788 pages
* Scala language specification: 191 pages
> Odersky himself gave up on scalac and he's writing a compiler and a new language from scratch.
Odersky created a new language to be able to do research without sacrificing Scala stability, which is already mainstream and should not undergo any more major revolutions. So Dotty is for research / incubating language features, while Scala stays on the stable side of things, letting companies like Twitter or LinkedIn develop without fear that 2.13 will not compile their 2.12 code.
> also poorly designed overall
This is an opinion, not a fact.
> With so many features that they interact with each other in ways that are pretty much unpredictable.
Name three. I'm coding in it for several years, and didn't notice a single one issue. I heard this complaint about Scala being too hard a few times very long time ago (when Scala was at version 2.6, and its tooling was in fact terrible), but it was always from programmers, who had also major problems coding in Java, so I never treated this seriously.