With #Java's evolution (discriminated unions, pattern matching, virtual threads), are #Scala/#Kotlin still worth it?

Scala & Kotlin have a culture of doing things at compile-time, the former more so than the latter. 

This yields safety & expressiveness, and is reflected in features that Java will never implement, in platforms that it will never target well, or in paradigms it will never embrace.

Java is still Java, and you're stuck with Spring, Hibernate, and Jackson, sorry.