IMO Tenuta's defenses were best against pro-style offenses. They stopped the run and put pressure on the QB when they worked, which was a lot of the time.
Just my opinion, but the advent of the spread and the ubiquitous speeding up on offense limits a lot of the complexity that one can deploy on defense. The QB can get rid of the ball faster and it's easier to see where to distribute it if you line up wrong while trying to bring some kind of exotic pressure. I am guessing this is why Tenuta didn't have a lot of success as a DC after GT. Just my theory.
I also think the current trend puts an emphasis on defensive depth and talent. To beat these hurry up spread-the-field offenses the best way is to keep it simple, line up right, keep your eye discipline, whip your man, and run to the football. You also have to be able to stay fresh and not wear down.