I’ve casually used Scala at work and home over the past 5 years. I mostly think this is because of the community and also the tooling and libraries.

WRT the community the functional zealots have pushed out everyone that doesn’t align to their ideology. Everyone that just wanted a better Java has moved on to Kotlin or back to modern Java.

WRT the tooling: scalac and sbt are so slow it’s painful and even IntelliJ can’t figure out what’s going on in Scala sometimes.

WRT libraries: every single time I have to upgrade play or the scala version there is a breaking change that either forces me to refactor or is undocumented and screws me at runtime.

So mostly at least for me, I’ve been burned by the language too many times to start a new project in it, especially at work where it will be long lived and I’ll eventually have to upgrade things.