Kotlin is better on paper but IMO, only the better choice on Android. I always run into Kotlin tooling issues on "non-android" Java. Stuff like Maven plugins not working. Plus, IDE support is only good in IntelliJ and it's been that way for years so I don't expect it to change.

Kotlin fixes tons of issues in the frankensteined Java 8 of Android. You can use Java 15+ everywhere else and its adopting many features that made Kotlin worth using.

Google is pushing Kotlin so they have control over Android language like Apple does for iPhone. It's just a nice layer over Java in the end since 100% interop is required.

Java is a long way from Kotlin feature-wise and at the current rate of "innovation" we're more likely to have expired before Java catches up with Kotlin. I mean, come on, in the 25 years since 1.0 Java hasn't even fixed the requirement to escape metacharacters in a regex. The SAM lambdas of Java 8 are also a feeble compromise with FP at best. Kotlin has a much cleaner approach to FP, immutability and null safety.