Enterprisey J2EE people regard it as a new fangled something they don't have time for.
More pragmatic, hip to it programmers seem to give more attention to scala, clojure, jruby.
Back when I was part of a project that was developing a JSF framework on top of RichFaces, I started pushing for Groovy support on our SDK.
This was 2009, Groovy was everywhere on JUG talks in Germany, most talking about Grails success stories. On the same year while attending JSF Days in Austria there were some Oracle guys showing how to do JSF applications in Groovy and the possible inclusion the the next J2EE revision.
Other team on the same company was replacing the Perl battle tested installation scripts by Groovy ones.
Nowadays, if it wasn't for Android Studio and its dependency on Gradle, I would hardly notice its use.
Our startup is writing "enterprisey" B2B knowledge management software, but almost all of our code is written in Groovy. But I'm "hip to it" enough to at least own several Clojure and Scala books and have both on my "to learn" list. shrug
Personally I'm a big fan of Groovy. It gets an awful lot of things right, IMO. The syntax is mostly a superset of plain Java, but a lot of things that are required in Java are optional in Groovy. But Groovy is dynamic and has meta-programming, closures, dynamic typing, etc. For my money, it really hits the sweet spot. Easy to learn for a Java person, but way more productive than Java.
Agreed, which is why it such a shame it isn't more prevalent.
Along with the features you mention, I'll add, good repl support, which is a must for modern languages in my book and is a huge productivity boost.