Marinelli gets more passes than any coach on the team. We've added more players to the defense than offense since he's been here. The excuses are tired.
What players have they added to the defense other than cast offs from other teams, problem players and the occasional late 1st rounder? There is not a DC in the league that will do much better than Marinelli given what he has had to work with. The only 1st rounder on that defense that regularly plays that I can think of is Byron Jones. Meanwhile, we give him a ton of guys that will barely see the field. Rolondo McClain and Randy Gregory get suspended for the year. Demarcus Lawrence was suspended for a while. Claiborne is forever injured. Sean Lee was healthy last year and is one of the best lbs in the league, but you never know how long he's going to be on the field. Barry Church was injured for a while last year and is a solid, but not spectacular safety. Wilcox is a hard hitter, but nowhere near elite.
On the other hand the offense has at least 5 1st rounders, and 2 of them taken in the top 10. It has 3 1st rounders on the O-line and that's not including Lael Collins who was projected to be a 1st rounder... Dez Bryant, one of the best WRs in the league. Jason Witten, one of the best tight ends to ever play the game. Ezekiel Elliott, who has the best RB in the league last year. There is a HUGE talent differential between the two sides of the ball. We even have Dak Prescott, who turned in arguably the best rookie performance in modern nfl history.