Seriously, fixing this can't be that easy.
If they're bad, it's actually pretty easy. But they keep getting 11-12 regular season wins and a postseason appearance out of these players and more importantly, coaching under MM and his staff. Granted, they're beating teams they should be beating, but they want a few against some tough teams too (see Detroit).
So we can't completely blame the culture, because how else are they winning divisions or wild card berths the past few years if the 'culture' were that bad, or the team was that soft? Dak is a 10 to 15 ranked quarterback in the NFL; he is who he is, and I think Dallas is getting the most out of them during the regular season.
So why then the complete implosion during the playoffs? Why can't this team, especially the coaching staff, turn it up a notch like others can in the post season? That's the question. They have no problem getting there; more than half the league has a problem getting into the postseason.
What's missing and how do you fix it WHILE KEEPING THE 11-12 WINS EACH YEAR?
I honestly think this is why Jerry, Stephen, and Co. are struggling with this.