John Carmack is a personal hero of mine, so it pains me to say this: Carmack hasn't produced anything noteworthy since AI was invented, therefore, how productive can it really be? It could be he is doing incredible work in private... but it could also be that he's lost in the weeds, because AI is so counterproductive while feeling the opposite? I remain a skeptic.
He's been spinning his wheels for a while. Carmack is a great example of how important working on the right stuff is. He's undoubtedly a brilliant programmer. Through him we get to see that a brilliant programmer working on non-programming tasks, can produce nothing.