I can only assume RC was so antiquated that Detroit didn't have any success last year with A Glenn running a defense with many similarities to those of the old Wrecking Crew. For about a decade, RCs defenses were very successful and one of the few defenses to destroy the run and shoot offenses of the day.

Leach had a unique offense and the NFL has adapted some concepts such as the mesh and the use of the slots on certain routes, but there is a reason why Leach was the only one running his version of the Air Raid. It was so extreme, many fundamental aspects of football were overlooked so he could try to outsmart everyone else. He held onto his offense long after other coaches took some concepts and combined them with more fundamentally sound aspects of football. He's very similar to Paul Westhead in college basketball. Innovative offense coaches who tried to go to extremes to get overmatched teams to compete against mediocre teams but never a threat to be a premier program. Both had some influence on the sport during their time, but both coaches were too committed to trying to outsmart everyone else and so their teams were very mediocre. There is a reason many Texas high school have adopted the offense. You can find success implementing it against more athletic but poorly coached teams. As players get better and the coaching improves, their systems aren't practical or affective.