I've only managed to use it as a linter-but-on-steroids because, where I'd normally page through the Ruby docs about enumerators to find the exact method that does what someone has implemented in a PR (because there's almost always something in there that can help out), I can instead prompt to look up a more idiomatic version of the implementation for the ruby version being used. It's easy to cross-check and it saves me some time.

It's not very good with the rest, because there's an intuition that needs to be developed over time that takes all the weirdness into account. The dead code, the tech debt, the stuff that looks fundamentally broken but is depended on because of unintended side effects, etc. The code itself is not enough to explain that, it's not a holistic documentation of the system.

The AI is no different to a person here: something doesn't 'feel' right, you go and fix it, it breaks, so you have to put it back again because it's actually harder than you think to change it.