On the other hand, I have tried them a number of times in greenfield situations with Python and the web stack and experienced the simultaneous joy and existential dread of others. They can really stand new projects up quick.
As a founder, this leaves me with what I describe as the "generation ship" problem. Is it possible that the architecture we have chosen for my project is so far out of the training data that it would be faster to ditch the project and reimplement it from scratch in a Claude-yolo style? So far, I'm convinced not because the code I've seen in somewhat novel circumstances is fairly mid, but it's hard to shake the thought.
I do find chatting with the models incredibly helpful in all contexts. They are also excellent at configuring services.
If all you're doing is something that already exists but you decided to architecture it in a novel way (for no tangible benefit), then I'd say starting from scratch and make it look more like existing stuff is going to help AI be more productive for you. Otherwise you're on your own unless you can give AI a really good description of what you are doing, how things are tied together etc. And even then it will probably end up going down the wrong path more often than not.
Especially, now that we do have models that can search through code bases.