Fail..

Kotlin is used on server side as well. There are mature frameworks (like Spring) which support its features natively. Also Kotlin is interop with Java, you can use easily every Java libs in Kt. It has many features Java should have been implemented years ago. So all in all it is an extended/better Java.

Java started to evolving too late but at least it started and many features are available now. Unfortunatelly it still need years...