I think the point is that comparing Scala the language to Java the language is apples-to-oranges. In general you are using Java along with a bunch of libraries (or Scala plus a bunch of libraries) so the question is whether Java plus all the libraries you are using is less complex than Scala plus all the libraries you are using. And the answer is not nearly as obvious as many people tend to assume.
For example, the most common thing people point to when talking about Scala's complexity is implicits. And that's fair because implicits can be hard to understand and can be used in wildly inappropriate ways. But I have found that what implicits are mostly doing (at least when used correctly) is taking stuff that would be implemented in Java with some crazy runtime reflection scheme and making it a compile-time construct. So then the question is not "are implicits complex?" but "are they MORE complex than the equivalent implementation using reflection?" And on that question I would say absolutely not! Runtime reflection is (to me at least) much more opaque, error prone and difficult to debug.
Implicits are just typed globals that you have explicitly ask for. Scala’s flexibility is the problem, we make scala code look like Haskell, or strange Java, or Idris. Very few people actually write scala sticking with their own pl linguistic baggage instead
For example, the most common thing people point to when talking about Scala's complexity is implicits. And that's fair because implicits can be hard to understand and can be used in wildly inappropriate ways. But I have found that what implicits are mostly doing (at least when used correctly) is taking stuff that would be implemented in Java with some crazy runtime reflection scheme and making it a compile-time construct. So then the question is not "are implicits complex?" but "are they MORE complex than the equivalent implementation using reflection?" And on that question I would say absolutely not! Runtime reflection is (to me at least) much more opaque, error prone and difficult to debug.