I’ve got no exposure to Kotlin, but I nodded along to and agreed with every entry in the list of “Scala [mis]features I won’t miss” at the bottom of this article.
What did you end up using instead of Scala?
I left the Scala role 2 years ago for reasons unrelated to the language. (I moved across the country and they wouldn’t agree to let me work remotely.) I now mostly wrangle infrastructure and coding isn’t my main concern. That said the language I’m most excited by is Clojure, although I haven’t used it in anger. I don’t enjoy the process as much, but I’ve had more practical benefit from writing Emacs Lisp (ox-jira.el & ob-applescript.el) than Clojure.