Life experience of seeing guest languages come and go, during the last 30 years, and never succeeding in the goal to replace platform languages.

On the contrary, platform languages slowly acquire the relevant features of the shiny languages, which eventually either fade away or find a niche for survival.

Kotlin will be relevant as long as Android exists, that is all.

Entirely replacing estabilished languages doesn't really ever happen, it's just the nature of the game.

Server software for unixy systems used to be near universally written in C and it's still "the" platform language. And it can be certainly be said that alternative languages have come and gone.

But: C has become a niche.

Scala, Clojure, and Groovy are all mature languages that haven't gone anywhere. No one has a goal of replacing Java, and they all benefit from improvements to the JVM.

Mere blips on the Java eco-system, why do you think Typesafe has pivoted into Lightbend and now also does Java projects?

Gradle and Google choosing it for Android are the only things that keeps Groovy still relevant.

As for Clojure, it is its own thing, plugging into the host platforms.

Of the JVM languages, AFAIK only Kotlin is making a serious push to get off the JVM using something like LLVM. Interesting idea, though I wonder how long they can preserve compatibility between JVM and native targets.

Scala native doesn't feel like it has the same impact, perhaps in part due to a lack of momentum (as I perceive it).

Clojure exists outside the JVM as well (ClojureScript, Babashka, ClojureCLR)

It does, but not in the same platform-antagonistic way. Clojure instead embraces many different platforms and runs on them through various dialects; Kotlin wants to become a platform.

Scala preceded it with both Scala Native and ScalaJS.