You're being silly. Nobody is saying Payton was perfect and there were many seasons where people were calling for his head. Payton has his flaws too. He was excessively loyal to bad coaches and even certain players and the team suffered at different points because of that at times. That was his fault. But he was also a great leader of men, master motivator and game planner. Better DCs could benefit from him being such a good offensive coach and I think DA being a great DC did benefit from that. Even with all of his flaws, he managed to accumulate 10 winning seasons and 9 playoff births in his time here.
There is much evidence that DA can coach a defense. He's very good at that. That said, who is DA leading and motivating? Which OC has he benefited by being a good defensive coach? Is there any evidence that he has ever made a team better as a head coach. I'm not saying he is for sure never going to do any of those things as a head coach, but I haven't seen it yet.