To underline just how badly Garrett is being out coached, even with a scoring drive, Dallas played right into Green Bay's hands. Green Bay gave Dallas the middle of the field and allowed them to take a good 5 or 6 minutes off the clock in a game where Dallas is down by 15 points. There was no urgency, no no huddle. Then it cuts to Jerr'uh in his box, dancing around after the TD, completely oblivious to the fact that Dallas first touched the ball in the second half behind by 15, and did not change that until 2 minutes into the fourth quarter.
McCarthy knows he isn't going to stop Dallas's offense entirely. So he did next best thing, he let Dallas run down the clock for him.
Also, to underline how inept Dallas is as a franchise; Jason Witten, a 14 year veteran, career long Cowboy and future Hall of Famer just scored his first post season touchdown of his career. It's sad Dallas did not give him many opportunities to do so much sooner.