I used to be very fond of Scala 10-15 years ago. I also had to move on for professional reasons and haven't kept up for a long time. I am very surprised that there is not much traction anymore for Scala. I see about 10x more Clojure news or projects on Github so it is not just about the JVM... Could someone point to why?
My impression is that, rightly or wrongly, it developed a bit of a negative reputation in various ways - too esoteric, slow builds, toxic community, etc. - so people stayed away from it. And meanwhile, Java the language improved and Kotlin came along as (arguably) the better better Java, so there became less of a need for it.
Scala was sold through Akka and Spark, solving pretty complex technical challenges that are less relevant nowadays. In fact if you can avoid Akka and Spark, do.
A lot of companies followed the hype without investing in the developer experience. Tech debt hurts more in Scala than in a bigger, slow moving language. After typical turnover, you get teams inheriting unmaintainable codebases. This leaves a bad impression. It can be avoided, Twitter built world-class SOA with Finagle, as well as a complete layer of libraries on top of Hadoop, at a time where the Scala ecosystem was even rougher.
The fact Databricks doesn't care much about the language also did tremendous damage, forcing the community to cross-build against very outdated versions of Scala.
In short, Scala was never a better Java and adopters who thought otherwise invariably got burned.