Kotlin is a light syntax for a coding style. It's as easy for a Java dev to learn Kotlin as it is to learn Spring or Hibernate or whatever library or framework the team at your new job uses
Even if Kotline were 'better' (And I don't think it is), it'd have to be quite a jump better.
It's a little nicer for getting ideas down quickly, but beyond that to me it's just 'different' and now a whole other bag of things to support.
If I have to chose between Kotlin+Java or just Java I'll take just Java.
Going back to Java from Kotlin there's really nothing I miss.