Didn't read the paper, but I think a charitable explanation of "too casual" could mean (a) ambiguous, or (b) technically correct but not using the expressions standard in the field, so the reader needs a moment to understand "oh, what this paper calls X that's probably what most of us already call Y".

But of course, I wouldn't dismiss the hypothesis of academically low-status language. Once at university I got a feedback about my essay that it's "technically correct, but this is not how university-educated people are supposed to talk".

(Okay, I skimmed through your paper, and the language seemed fine. You sound like a human, as opposed to many other papers I have seen.)