Dallas defensive rankings by year:
https://www.pro-football-reference.com/
2016 - #5
2017 - #13
2018 - #6
2019 - #11
2020 - #28
So Dak had a top 5 and a top 10 defense in two seasons, and a top 15 defense twice. The only year he had a god-awful defense was in 2020.
SOMEONE PLEASE TELL ME WHY DAK KEEPS GETTING THE POOR DEFENSE EXCUSE WHEN HIS DEFENSE WAS BAD ONLY 1 SEASON..........
If you think this defense was really all that good in any of these years, I have some swamp land to sell you.
2016 was an aberration. They were 5th in points per game but that was largely a by product of the fact they controlled the clock and kept offenses off the field. For example, in that year, their points allowed per drive was actually much lower around the mid teens, I believe. That's because they weren't a very good defense at stopping people from scoring. They were mediocre. They just didn't face the number of drives many other defenses faced.
Go further. The Top 5 points allowed per game defenses were: Patriots, Giants, Seahawks, Broncos, Cowboys. Now look at their points allowed per drive.
NE was #1 in points allowed per drive
NYG were #2 in points allowed per drive
Seahawks were #4 in points allowed per drive
Denver was #3 in points allowed per drive
Cowboys were #14 in points allowed per drive
Who is the outlier there? Cowboys were #1 in time of possession that year, I believe. So in reality they protected what was a really mediocre defense. Same thing in 2018. They were 6th in points allowed per game but 13th in points per drive. Again, they just churned up clock and kept the other team's offense off the field.
This is not a defense of Dak mind you. But it's to point out this myth that the Cowboys had really good defenses a few times in the last few years is not really an accurate statement.