In order for you to properly guide it through a refactor, you have to understand the code, which becomes less possible as it grows into a mess of spaghetti. I think that's just setting yourself up for a massive amount of frustration. When there are multiple systems that need a refactor, each individual refactor becomes that much more complicated. And trusting the tool that created the mess to sort it out seems a tad delusional.

It's true that AI has an incredible ability to take in a massive amount of information and do useful work with it. But it has no direct ability to exercise judgment, and with each iteration of reasoning and applied changes, its ability to hold the original intent degrades very differently from a human intelligence.