Here's the issue...
Jerry's culture is one of celebrity. Celebrities don't want to follow the rules, they want special treatment.
McCarthy is a fraud, but at his very best, he's a players' coach. He is not a disciplinarian and even if he tried, he'd be undermined by Jerry.
Zimmer is tough as nails. He will be undercut by Jerry as well but it's his own fault if it happens. He knows exactly what he just signed up for.
Players as leaders you ask?
Dak? He's a rah-rah guy, just like Jason Witten was. He'll blame himself and say we have to do better, all the cliches. But because they are always rah-rah, there's no validity or merit to it. It's background noise, especially in the heat of battle.
Micah? Talented beyond all belief. Emotionally? He's immature and he says things without thinking them out. He's more likely to burn it all down than he is to build something special.
CeeDee? Super talented but he has the WR diva gene. I think his heart is in the right place; his body language makes him to hard to take credible as the guy you rally around.
This is the Dallas Cowboys and the environment that Jerry has created.
Leadership 101: You are either teaching it or allowing it to happen.