While I acknowledge that Scala is a superior language to Java, I believe you are turning a blind eye to Kotlin and C# here just for the sake of Scala.

What Java really is is a an easy to learn OOP language that conforms to what most people learned at university. Die hard Java folks don't want Scala, they want a better Java. They don't want a new paradigm, they want a better Java. They know Scala is better, but that is not what they want. Having worked with many Java devs, it is very clear to me that they don't want a better language, they want a better Java. That's why Scala doesn't cut it.

What really looks like a Java++ is Kotlin. However, Kotlin got too tied up with Android and lost the opportunity to take Java's market share. JetBrains also didn't do a very good job at creating frameworks to make it more relevant.

C# is a Java++++++, but spent too much time tied to Windows. However, things changed. .Net 5 is truly amazing and crossplatform. I really urge you to try it and set aside any prior judgments over C#. Either for being closed-source (which it isn't anymore) or being Microsoft (which is one of the most dev-friendly big tech of the moment).