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.