Earlier quoted context omitted.
But... When Java gets "properly engineered solution" for async code... Kotlin got it as well!
So why bother using Kotlin? Seems like it fixes trivial things (makes simple classes a bit more terse) but retains the more fundamental problems and hangs on for Java to actually fix those.
Kotlin syntax makes writing functional code beautiful and simple... map and fold and filter are so much easier to write than in any other language that also have the same functions, such as JS. Again, that alone would be enough to migrate.
But there are still so many more simple, but incredibly useful functions like SubstringAfterLast which takes a nasty, ugly Split function into a beautiful, precise line of code. Just one example of many.