Java has adopted maybe 20% of the things that make Kotlin better, but due to backwards compatibility it'll never catch up.
Personally I think it'd almost never make sense to adopt Java over Kotlin for any greenfield JVM project, unless the devs you hire are truly so low-skill they can't pick it up.
Kotlin supports neither structural pattern matching nor guarded patterns as they are available in both Java 18 and Scala. It's Kotlin that needs catching up nowadays.
It's an abstraction atop Java. Of course it plays the catch-up game. It inherits new features from Java. They can't have it instantly.
> They can't have it instantly.
Why not if Scala did it way before pattern matching was introduced into Java?
Null-safety.
Read-only interface by default - `MutableList` vs `List`.
if-expression, they just look nicer than `a ? b : c`.
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You're right that Kotlin is not an "abstraction atop Java (the language)". It's meant to be a better Java that feels familar to Java. With that rationale in mind, it's reasonable that they left some features from FP languages out of Kotlin.
As I have said in another reply, it was a great decision to not follow what Scala did with pattern matching.
`if (o instanceof String s) {`
Not much benefits over Kotlin's smart casts.
Guarded patterns with this version of pattern matching should be translatable to adding another "and" condition. The Kotlin compiler should have no problem reasoning with that.
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I find positional destructuring in Scala (which works similarly in Java 19) a bad design.