This is an interesting point, and I think its this: the days of dominant defense are just over. Do you remember the "Iron Curtain" Steelers defenses of the 70s, the 1980s Giants with Lawrence Taylor, the mid 1980s Bears defense with Richard Dent and Mike Singletary, the early 90s Eagles D with Reggie White, Jerome Brown and Seth Joyner, the 1990s Cowboys defense with Charles Hayley and Deion Sanders. These were D's that would utterly dominate games, regularly holding opposing offense to less than 20 points, sometimes less than that.
And there is nothing like now. NOTHING. Best you can hope for are "bend don't break" D's, D's who cause just enough disruption to allow their team to win. I mean, the Rams probably have the best D in the league, and they are far from complete.
Maybe its by design by the NFL? Audiences would match rather watch aerial dogfights like yesterday's game than a 13-10 defensive slugfest.
But yeah the dominant defenses of all old appear to be extinct.