Griese was a Pro Bowler 4 of his first 5 years, first team All Pro in 1971. So actually it was like losing a top quarterback.
Morral was in his 17th year on his sixth team, and had not performed as a top 10 QB since 1968. Obviously he played well in ‘72 but it wasn’t a sure thing with no expected drop off by any means.
The number of pass attempts is desperate weak sauce. It was a different game pre-1978 rule changes. They led the league in yards per passing attempt, finished first in total offense, points scored, total defense, points allowed.
Relative to their peers, they were a dominant team. Their third best rusher (Kick, 521) would have led a handful of teams in rushing, Csonka and Morris had 1K, the defense was outstanding. They didn’t pass because of the era and they controlled games so much there was no need to; why fix what ain’t broke?
This is like defending Trump because people insist on hyperbole. They’re not the best team in history, so what? They still get to enjoy their unique accomplishment.