Modern Java is usually 100% XML free. Even new servlet containers/standeard REST frameworks (Dropwizarrd, embedded Jetty etc.) require no XML whatsoever.
You only need XML if you're deploying to heavyweight servlet containers (standalone Tomcat, e.g.). Even embedded Tomcat doesn't use XML.
That's not what I wanted to point out. To write a POM, you don't need to know the XML specification. If you want to write a Gradle script, you don't have to know Groovy. You just have to use the Gradle DSL which is fairly compact for most plugins. You make it sound as if you have to learn a whole new programming language, and if that was the case I would agree that Gradle sucks! If you want to do something more specific, then yes you will have to learn Groovy, but at that point the time will be spent well. Also, most of the time Groovy is weakly typed Java with lambdas and no semicolons. I think you've already spent more time arguing about not wanting to learn Groovy than time you would've needed to learn said amount of Groovy.
Maybe you can write it, if it's a solo project with a fairly vanilla build. But as soon as you have to collaborate with other people, or read examples from the internet, you're going to run into full-on Groovy; "the Gradle DSL" is not well-defined, so while most bloggers will claim they're writing idiomatic Gradle, they'll all have different subsets of Groovy in mind when they say that.
By contrast Maven has a very rigid format - there's no risk of randomly seeing a lambda or conditional expression in the middle of the XML - and its plugin model ensures that there's a very clear delineation between what's standard and what's an extension.
The "Gradle DSL" and Groovy's grammar are the same thing, mixed together in one Antlr file, and probably the largest programming language grammar I've ever seen. Here it is for Groovy 1.8, the version that shipped the paren-less parameters that Gradle uses:
