I find Java 21 very pleasant, as long as you figure out how to avoid ugly things like Spring’s autowiring of dependencies.
I haven’t really given kotlin a fair try, but I find it ugly the couple times I’ve tried to work with it.
What I’m really curious about: do IntelliJ’s refactorings work as well for kotlin as Java? I find the refactoring tools make up for Java’s shortcomings as a language.