"[Scala] is essentially a write-only language (please don't quote me on this!); " I'm sorry, I quote you on this. If you ever compared Hadoop codebase (Java)

"[Scala] is essentially a write-only language (please don't quote me on this!); " I'm sorry, I quote you on this. If you ever compared Hadoop codebase (Java) with Apache Spark codebase (Scala) you'd know this is BS - Spark code is order of magnitude more readable and easy to understand compared to Hadoop. Lack of side effects and lack of low-level mutable shared state protected by locks everywhere are two of the many reasons. Of course, you can write terribly unreadable code in any language, and probably those academic languages with rich functionality and expressiveness make it a little easier to abuse features, or to choose right features for the job. But on the other hand I'd argue they make it easier to write readable code, once you care about readability and learn how to do this. Writing readable code is a skill you have to master. It is not something that comes for free in no time.