Scala 3 slowed us down?

I was involved in a Scala point version migration (2.x) migration a few years ago. I remember it being painful. Although I recall most of the pain was around having lots of dependencies and waiting for libraries to become available.

At the time Scala was on upswing because it had Spark as its killer app. It would have been a good time for the Scala maintainers to switch modes - from using Scala as a testbed for interesting programming-language theories and extensions to providing a usable platform as a general commercially usable programming language.

It missed the boat I feel. The window has passed (Spark moved to Python and Kotlin took over as the "modern" JVM language) and Scala is back to being an academic curiosity. But maybe the language curators never saw expanding mainstream usage as a goal.

Outside of Android work, has Kotlin really taken over? My understanding is that Java added a lot of functional programming and that took a lot of wind out of Scala's sails (though Scala's poor tooling certainly never helped anything).

Java's new features are always going to be on paper. The ecosystem, with all its legacy code, is always going to be a decade behind. And if you are starting a new project, why would you pick Java over Kotlin?

That's kind of what I'm asking. I did have a former co-worker write a micro service in Kotlin around 2018. He said that as nice as the language is, the ecosystem was (at the time, not sure how it is today) so utterly dominated by Android development, that he said he wouldn't recommend using it again - half the time he was calling out Java anyways.