If you've given up on understanding your code base, AI will give you a better solution than you could come up with. Not because AI is better, but because you've become a low performer.

AI is reasonable at reviewing code, with only a 50-60% false-positive rate, and its persistence at broadening scope often finds things human reviewers would miss. It's still actually still pretty shitty at writing code, though, again, with enough ground truth and persistence, it'll often generate something that's a functional turd. It will sometimes come up with better suggestions if you prompt for it, but it needs a ton of hand-holding at the moment. And usually the suggestions are still overly complicated messes that you can trim down to 1/10th the size, while keeping the core idea.