To clarify, AI should not do the design itself. You develop the design in conversation with AI.

I come in knowing what I need to build and at least one idea or more of how it should be done. I present the problem, constraints, potential solutions, and ask for criticisms and alternatives. I can keep it as broad as possible or I can get more granular like struct layouts, api endpoints, etc. I go back and forth until there's an approach I prefer and then I code that approach.

| it can code pretty well given a very tight and limited scope.

It's wildly better at tight and limited scope than large scale changes but even then I would rather code it myself.