It is telling that the most high-profile, most-widely-used Groovy project has chosen to rewrite their own code into Java for performance reasons, and is touting the ability for end-users to write build scripts in Kotlin instead of Gradle to get better tooling and performance.
I contend that Groovy is the "bash" of the JVM: there may be use-cases for it, but it's so prone to becoming a minefield that you're often better off using a more fully-fledged language (one that's not so slow and doesn't aggressively hide errors from you in the name of being "dynamic")
He actually meant "Kotlin instead of Apache Groovy". Groovy joined the Apache Software Foundation last November (2015), and its name should be qualified with the "Apache" brand on first use in a new context such as a webpage. Groovy joined the ASF after the 6 developers working on it and Grails were retrenched by VMware in March last year, and they couldn't find any other business to support their work on Groovy.
I contend that Groovy is the "bash" of the JVM: there may be use-cases for it, but it's so prone to becoming a minefield that you're often better off using a more fully-fledged language (one that's not so slow and doesn't aggressively hide errors from you in the name of being "dynamic")