That works great for a small greenfield project. Now try applying it to a million-line monorepo with three competing architectural patterns and a CI/CD pipeline that breaks if you look at it wrong. The real world of development is much messier

If you have such a beast you have n problems. Not being able to apply AI to it is just (n+1)th.

It works great when dealing with microservices architecture that was all the rage recently. Of course it doesn't solve it's main issue that is that microservices talk to each other but it still lets you sprint through a lot of work.

It's just that if you engineered (or engineer) things well, you get immediate huge benefits from AI coders. But if all you did last decade was throw in more spaghetti into already a huge bowl of spaghetti you are out of luck. Serves you right. The sad thing is that most humans will get pushed out into doing this kind of "real development" so it's probably a good time to learn to love legacy, because you are legacy.