I see a very slow Defense today. Unless these guys all of sudden shave a full second of their 40 times, they will not be a top 10 Defense...
You see guys look slow.
Here's what I see:
While the offense is preparing to get set, I see the coaches relay in an algebra word problem. The defensive players then solve that problem (some alone, some together). When they're done, they're allowed to go stop the ball.
At times, that process looks slow.
You are about 80% right with that IMO. While mostly its the scheme, what they are asked to do and the fact that they can't just run on instinct.
However, they are still slow and you can see it in pursuit and closing on the ball. Remembering the kind of speed we used to put out there in good ole days that was the biggest thing that stood out. Even when the defense broke down what would be a 50 yard gain was kept to 15 yards because we had too many guys that would close to the ball and fast even with bad angles. Now you see the opposite. You see guys running in quick sand trying to corral mediocre players on the opposition.
Safety is probably where you see this lack of speed the most Crawford, Jenkins and Carter are on the slow side.