And for the Sytem to work, you need some guys who just buy in and do their jobs play in and play out, but you also need a few great athletes to truly make it work.
It worked for BYU at a high level the same way it did for Pittsburgh--when they had 1 DE that could get to a QB, had 1 OLB that could get to the QB, and 1 safety that made plays all over the field. And when the front was disruptive enough to force TOs.
Take away those elite elements, and the D is easier to take apart and forces fewer TOs.
So the answer is--you need both.