Where I work we use Groovy heavily for testing (with the Spock Framework - which is amazing), in our Jenkins pipelines, and for Gradle Plugins in our build.
I see a pretty active community around it and lots of new releases (from the libraries and the language itself) coming up all the time. Your picture of Groovy being dead couldn't be more wrong in my experience.
A programming language is alive as long as there is one developer using it, doesn't mean it still matters at scale.
As mentioned, Gradle is still around.
Gradle is moving more and more towards kotlin
Had it not been for Gradle, and there would be hardly a reason to learn it in 2021, other than historical interest.