I thought Sanjay Lal made an excellent point in his comments:
"The whole premise, in my opinion, of this offense is vertical speed," Lal said. "If you can't hit a go-route, the comeback game isn't real, your slant game, your nine-stop game isn't real. Being able to hit those deep balls in games is going to change everything if we're able to do that."
I believe that was one of the huge problems this passing game had, they never challenged opponents deep. And if you can't or don't do that, opposing defense won't fear or respect your passing game, and they'll simply sit on everything short. And that hurts your running game with having more bodies closer to the line of scrimmage, as well as your passing game with defensive backs sitting on routes.
It will be huge if the Cowboys can start to scare defenses down the field again.