The Quality of Marciano's Opponents

You are defending a premise that has not been attacked.
Moore's wins over Maxim and Durelle were at LHvy.
Olson was a middleweight.
Rademacher was never a ranked heavyweight.
Who did Mathews beat at heavyweight,who wasn't already washed up? Lastarza was a protected fighter, he beat a couple of names who were past prime,and avoided all the iron of the division.

 

..ad nauseam..

 

About 30 of those 43 fights Rocky had were against no-hopers and journeymen because he had a very short amateur career and was very raw and clumsy. Goldman spent a lot of time making sure Rocky got the much needed experience and rounds under his belt before having him step up in class.

This is not the same as the traditional old school route where fighters would have a lengthy amateur career, then gradually increasing the difficulty of the opponent level every 15-20 fights, then remaining at the elite level for half a decade or so. You're right in that Rocky got the hell out of there once his body began to break down, and that's the crucial difference between himself and his best opponents like Charles, Louis, etc who not only had much longer careers, they had even more wear and tear from the amateurs, tons of exhibitions, brutal sparring, and continuing to fight multiple times a year.