This type of thing is targeted towards enterprise and the usual large and well-established environments.
Environments where replacing a 20+ year old app written in COBOL isn't a question.
No one is ever going to say "Let's write this new app in Groovy!". On top of management saying "WTF is Groovy?", it'll never get approved because it's a huge amount of technical risk to take on.
In big enterprise, you want to have your stuff written in the most supportable language you can find resources for. This is why Java is so popular - it's a lot easier to find a Java developer than it is someone who knows Groovy, Rust, Scala, etc.
By mentioning Apache Groovy in the same breath as Cobol, Java, Rust, and Scala, you're comparing apples and oranges. Groovy is to the JVM what bash is to Linux. Groovy is a dynamically-typed language, best used for writing scripts used for glue code, testing, build control, and what not, whereas those others are statically compiled, used for creating actual systems. Although static compilation was added later, virtually no-one uses it.