As the most extreme counterexample of your ... experience[1], someone made a plugin that allowed writing pom files in languages other than XML: https://github.com/takari/polyglot-maven/tree/polyglot-0.7.2...

With an especial nod to https://github.com/takari/polyglot-maven/tree/polyglot-0.7.2... given this submission

1: I believe that you encountered errors, programming is packed to the gills with them, but correlation is not causation in that just because it did not immediately work in your setup does not mean it's impossible or forbidden