Google is the one to blame, they let Android Java stagnate on purpose, after all it helps to sell Kotlin.

Kotlin is free though, and a JetBrains product, not a Google one.

Kotlin is married to Android, it doesn't go anywhere unless JetBrains settles for a divorce.

Actually, they've done a pretty decent job on multiplatforming it. Can use it for servers, compile to JS, even compile through LLVM and target iOS if that's your jam. Android is the killer use case, of course, but I think it'll survive losing preferred status on Android.

There are dozens of languages that have done exactly the same and eventually faded away.