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There are rules advantages to the passing game in the modern NFL.
Most flags on a passing play are on the defense.
Most flags on a running play are on the offense.
You can complete a pass without completing the pass which makes it more efficient than in golden days.
This simply cannot be understated. Other than offensive holding (where you don't lose a down), there really aren't any penalties called against the offense. There are a slew of defensive penalties that can now be called, and darn near all of them carry an automatic first down.
Those old Peyton/Colts teams had it right, they just didn't have the postseason QB to pull it off and win a ton of Super Bowls. Well, and Tom Brady.............
Throw it all around on offense with a HOF QB, and build your defense with DE's 1st, a solid secondary 2nd (either by talent or by scheme), and fast LB's 3rd.