Just as the Cowboys built their offensive line with 1st round draft picks, Washington built their defensive line with 1st round picks four years in a row, from 2017-2020. This year, they drafted a LB in the first round.
The Cowboys team of the late 70's featured a D-line with 3 top 5 overall picks and then Harvey Martin.
The 90's Cowboys starting D-line was composed of two DT's that were drafted #1 and #2 overall, Russel Maryland, and Tony Cassilas.
The defending SB champion Bucs have a DE drafted #2 overall and another DE a mid round 1st.
You have to invest premium picks and cap space to build a defensive line and the Cowboys have tried to an extent. The Cowboys have drafted a D-linemen in the top 3 rounds in 7 of the last 8 drafts. However, when you go below the top ten overall, that requires an excellent ability for scouts and coaches to collaborate and come up with the right player based on perceived talent and need.
This is where the Cowboys fall short. I think they are great at evaluating college talent but fall short on how that player fits into their system. It certainly doesn't help if they change systems every year. They have done a very poor job in veteran free agency when it comes to the D-line with the exception of Quinn and they failed to find a way to keep him for more than 1 season.
Not including this year's draft, the Cowboys have Lawrence and Gregory, both #2 picks that were projected as 1st were it not for some "baggage". They have Hill and Gallimore at DT, a #2 and #3 respectively.
This season, the Cowboys drafted two D-linemen in the 3rd round. They may not have invested a series of #1 draft picks, but they obviously respected the squad enough to do the second best thing.
I don't expect the line to be dominant but I do think they will be more consistent based on their ability to stay healthy. The important thing is that the improvement on defense won't come from the rookies as far as the D-line is concerned. It will come from players that you expect the most, those in their second and third years. For all practical purposes, you can throw Gregory in with that group.
Gallimore and Hill are key. If they can both show a significant level of improvement it will go a very long way to insuring the Cowboys have a successful season.