I don't think AK has said anything like that. He certainly called out the offensive system and play calling, but I don't think he's said anything bad about DA. But, I could have missed it.
And, I don't disagree that he has been a failure as a head coach and I would have let him go two years ago. But, I don't think his failures are about not being a "leader of men." There are lots of ways to lead and clearly DA isn't the Dan Campbell type, but there are many different kinds of leaders. And some leadership is not obvious from the outside. Personally I think DAs failures have more to do with too much loyalty to PC and his failure to get a new OC when he was hired, bad in game management, and an inability to manage difficult players like MT and CJGJ.
I guess my point is that there is no way for any of us to know if DA is a leader and if he is what kind of leader he is. For some, like Dan Campbell, Sean Payton, Mike Tomlin, etc. it's obvious. For others you really don't know unless you are inside the team.
I also think DA has fallen victim to our over expectations of the post Brees era. Due to lack of players or injury, we basically had not QB on this team until last year and Carr was bad to average for most of the season until he got it going in the last 5 games. Moreover there is no real pass rush and the OL is mediocre at their best. But, our expectation, built during the Payton/Brees ear, is that no matter the holes on the team, you just overcome them. That's not going to happen if you don't have an elite QB. Still, I think DA should have done a better job than he has done and maybe he would be on the right track had he hired a guy like Kubiak when he was hired for the job.