I only added in the sacks just because it's a silly stat that everyone loves to point to for effectiveness in the passing game, but he's a critical player even without the sacks cause he's doing literally everything. Watch him play and tell me the plays he's making aren't unique to his skillset and aren't absolutely crippling the opposing offense's gameplan. His main attribute is his sideline to sideline speed blowing plays up. How many passing plays in today's game are short passes that are set up? There's a million underneath passes to WRs, tons of plays to running backs that aren't just screens. Stopping teams on 3rd and 4 or some other short down like that wins you games. Tackles for loss are pretty much as good as sacks. 3 and outs are the best thing you can do next to an immediate turnover or a defensive score. It's way better than getting drove on for 5+ minutes and then getting a turnover.
Elite LBs are multi-dimensional and are very hard to find. They need to be versatile enough to manage the entire field, rush the passer, stop the run, shed blocks, cover TEs, cover WRs going underneath/over the middle, make proper reads in the red zone, etc. There's obviously way more but this is just a quick post, so whatever. An LB with high football IQ, great size/speed combo, great tackling and coverage abilities is a blue chip athlete. Extremely difficult to find this skillset in later rounds. You can find pro bowl DEs/DTs more commonly in later rounds. The main issue with the position is staying healthy, which is a major knock on safety as well. Players like Patrick Willis or Luke Keuchly are very hard to find and transform a defense into elite units.
The sack vs NYG is absolutely a legit sack because of his skillset btw. Look at what he does, he fakes like he's dropping and then has the speed to completely destroy the play and get the sack. Huge element for the opposing offense to be forced to gameplan against anytime he's standing in that spot. There's a lot more to a team being a successful defense than just winning 1 on 1 battles in the trenches.
I don't really understand how a Cowboys fan can undervalue the linebacker position. We've had first hand experience for years watching the defense go from pretty good to absolutely horrendous based on the single notion of whether Sean Lee was playing or injured that week. Lee was pretty much Tyron Smith's in/out impact for years in his prime. It's not easy to plug in a random 5th/6th+ round linebacker to weather the storm for a few weeks.