You can't compare scoring from the 70s to todays game and draw any conclusions. You need to compare that team to other teams from that generation. I tired finding CFB defensive stats from 1971, but none exist in aggregate.
For example, the Alabama team we beat in the Orange Bowl that year only gave up more than 10 points 3 times and more than 20 once (to Nebraska), same as NU. Not sure they are "one of the best defenses in the history of college football".
Agree with this. Not only are offenses completely different but the parity of college football now makes the overall schedule a lot tougher. Back in the 70s and 80s, we were simply physically dominant over most of the teams we played in any given year. Even the 1976 team - which was a "down" year by those standards, going 9-3-1 and 4-3 in conference - only gave up more than 14 points four times and averaged just under 14 ppg given up for the year.
I am not so sure that we play a tougher schedule now. Nebraska played a tough schedule in 1971. We beat the teams ranked 2,3 and 4 in the final AP poll.
Not saying certain teams we play are better. But the overall quality of the teams we play is better. Instead of having 2-3 really tough games and a bunch of teams that we beat simply by showing up, we - and everyone else - play 9-10 games against teams that *could* beat us if we don't play well. We're still expected to win most of those games but we don't have the third-stringers in by late in the third quarter.