Kotlin is surprisingly good if you cannot afford Scala. It's less divergent from the Java ecosystem and doesn't introduce anything conceptually new. But it's not that popular on the backend.

The only thing about it I personally find very unpleasant is its idiomatic approach to concurrency. In the world of Futures and go routines continuations are such an outlier.

I find it hard to remember more than one company I have interviewed with in the last ten years using Clojure. It was hyped together with Erlang in 2009 or so and nobody remembers either.

I'm actually working in a Clojure job at the moment, but they're definitely hard to find. Scala is far more common.

I feel like my Java skills improved greatly after switching to kotlin, because it made me realize how much more code I'd have to write for the code to be nice. The simplest example would be "val x = ..." vs "final String x = ...". Sometimes I just wouldn't bother with the "final" keyword, but now I cannot let mutability ruin my code.