I have no real insight into your personality and ability (but neither do you about GF).

Competent people who want or need to fix some dysfunctional monstrosity committed by a coherent group of less able developers are not necessarily welcome, even if they don't have pathological personality traits. All the more if they are not parachuted in to fix something, but e.g. some new starter not high up in the hierarchy. Consider that few people take kindly to being told (if only by implication) that what they've done is garbage, but obviously the world is full of garbage software.

I've seen this time and time again. Long-term diplomacy can sometimes work (assuming the company and individual have the time to spare), but they'll usually need some higher up backing or fail miserably/leave/get-fired.