When comparing teams from different eras, I think you need to compare them to their peers. For example, in today's NFL, the '72 Dolphins would be tiny and slow. But, compared to their peers, they were incredibly dominant.
Everyone knows how good the no-name defense was. Bill Stanfill was a perennial Pro Bowler. Nick Buonicounti is a HOFer. Dick Anderson and Jake Scott were the best safety tandem in the NFL. As good as they were as individuals, the unit as a whole was even better. But, people who underestimate the '72 Phins usually do so because they think of the offense as not being explosive, but consider this:
A HOF QB
A HOF FB
A RB with one of the highest avg yards per carry in league history
Another RB with Pro Bowls on his resume
6 Pro Bowl offensive linemen
2 TEs that combined to win seven Super Bowl rings
A HOF WR who was the only receiver in league history to retire averaging 20 yards per catch, and was once 5th all time in TD catches
Another WR who held most NCAA receiving records at the time