I'd put XML and annotations in the same class of problem because they are (mostly) not checked by the type system. For instance, you can have a REST controller

I'd put XML and annotations in the same class of problem because they are (mostly) not checked by the type system. For instance, you can have a REST controller that simply does not "work" because you're missing an annotation. You can easily debug this if is a place in your code where the controllers are registered, but with annotations the interactions between your code and the framework (or whatever requires annotation) are not obvious by just looking at the code.