Looking around the office and my phone, Java is anything but "legacy".
As for alternative JVM languages, while they are cool and have brought many fresh ideas into the platform, they remain a very tiny portion of the Java developers' market.
Java takes a very long time, because backwards compatibility and cooperation among giant companies takes years.
C# has basically Microsoft deciding how the roadmap looks like and rebooting the platform multiple times.
C# 8 won't even be fully supported on the .NET Framework.
As for alternative JVM languages, while they are cool and have brought many fresh ideas into the platform, they remain a very tiny portion of the Java developers' market.
Java takes a very long time, because backwards compatibility and cooperation among giant companies takes years.
C# has basically Microsoft deciding how the roadmap looks like and rebooting the platform multiple times.
C# 8 won't even be fully supported on the .NET Framework.