Defenses have won championships recently in the modern NFL, though. And one of them may yet be what wins this year's Super Bowl, so it's silly to pretend you already know what the story of this season's championship is based on the regular season or some divisional round games.
We may see a Super Bowl this season won by defense. Maybe it's a reckless shootout, sure. Or maybe the narrative of this year's championship ends up being that the Pats' figured out how to stifle McVay's offense. Or that Wade Phillips' defense handed Brady the kind of loss the Giants' defenses did. Don't assume you already know what the story on this season is. One of these defenses shutting down a Brady offense or a McVay offense will result in the narrative being about that defense winning it.
Look at Peyton Manning's time in Denver. It was their defense that won for them in the year they won their Super Bowl. Manning was terrible in 2015, the season they won it all. That was their defense, all the way. The year they lost the Super Bowl two years earlier (when Manning and the offense were elite), it was because their amazing offense ran into the buzzsaw that was the Seahawks' defense.
Look at those Seahawks. Their defense was amazing the year they won it. Their defense alone outscored the high-flying Broncos offense in that Super Bowl with a safety and a pick-six, and that was the year Peyton threw 55 TDs and led an insane offense. When the Seahawks lost to the Patriots, it was the Patriots' defense slamming the door on them with that takeaway to win the game.
Speaking of the Patriots... their 0-2 record against Tom Coughlin's Giants in Super Bowls is almost entirely thanks to the Giants' defenses picking off and harassing Brady and holding the Pats to under 20 points each time.