One thing the Java architects have said is they let most of the complex feature development happen outside of Java, which is pretty nice.

They let the likes of Kotlin, C#, C++, Scala, Haskell, etc all explore their own little features then they figure out if it could be integrated with Java and what it'd look like.

I really like that approach because it's slow, methodical, and the features typically are very well aligned with Java. None of them feel particularly out of place.

Java's preview system also works pretty well to get these features refined over time.