I use ChatGPT the most when I need to make a small change in a language I'm not fluent in, but I have a clear understanding of the project and what I'm trying to do. Example: "write a function that does this and this in Javascript". It's essentially a replacement of stack overflow.

I never use it for something that really requires knowledge of the code base, so the quality of the code base doesn't really matter. Also, I don't think it has ever provided me something I wouldn't have been able to do myself pretty quickly.