the core role of an engineer in many ways already is validation of a plan.

I disagree, this implies that AI are doing a lot more than they actually are. Before you design the physical layout of some thing, you have to identify a problem, and identify guidelines and empirical metrics against which you can compare your design to determine efficacy. This is half the job for engineers.

There’s one step of the design process that I see current AI completing autonomously (implementation), and I view it as nontrivial to get the technology working higher up on the “V”.