They have been trying to do this for years with the best offensive line and best RB in football, that is an offense that hasn't scared anybody with that approach. Even this year they were sputtering until they got the receiver from the Raiders, Cooper.
Sure, it has had moments, but the teams that do it the other way, throw it to keep 8-9 out of the box so when they do run, they can run effectively, those are the teams that have had the great offenses.
The Cowboys are 24th in points and 23rd in yards. They are 4-1 team since Cooper was acquired and it helped some, but that approach just typically doesn't work because it typically plays out like this.
1st and 10 - run for 1 yard
2nd and 9 - run for 1 yard
3rd and 8 - other team loads up and gets to QB for a rush or sack because down and distance is bad.