I'm not a coach but if the D line can't get to the QB I see why you play off the receivers. That way you don't get a bump and run with a guy loose down the field and the QB sitting there waiting for it to happen.....but why not bump and run then confuse the middle with surprise blitzpackages and or play 2 safeties to roll over to the outside to pick up deeper routes and have an LB play an inside route if receivers break in the middle? Am I missing something?