Afaik, at the time issue was a lot of programming in xml - where those frameworks are configured in various xmls and hard to understand and maintain. Reflection based frameworks are later development.
The massive amounts of indirection which the IDE wouldn’t help you understand was the difficult thing. What encoding you use for that is pretty irrelevant. JSON would have been worse.
The indirection in Java itself matter significantly less, because you ctrl+click and it gets you where the things are. Plus auto completion. Both were part if Eclipse years and years ago.
The problem with xml was that IDEs were unable to help you.
