Java is good enough and Kotlin does not add anything substantial worth of switching. Google provides first-class support for Kotlin. Oracle does not. Kotlin do

Java is good enough and Kotlin does not add anything substantial worth of switching. Google provides first-class support for Kotlin. Oracle does not. Kotlin does not evolve with JVM. For example they introduced coroutines to imitate blocking code and few years later Java decided to create green threads, making the feature essentially obsolete. Kotlin made sense in Java 1.7 time, when Java seemed to be stale and kind of dead. Things changed since then.