Nat was clearly bias against the 40s and 50s which is crazy because they were much better eras than 1900-1920
Damon Runyon died in 1946. Grantland Rice died in July 1954. Rice also was more a college football, golf, and baseball writer, with boxing a sidelight for him. Sort of odd appeals to authority. I remember Dan Daniel writing an article on Dempsey and mentioning that the only time he actually saw Dempsey live was the Toledo fight.
the guys that fought him claim he was not that easy to hit clean. I think the distinction would be that Marciano fought fine boxers that were also darn good punchers like Walcott, Charles and Moore, while Dempsey was beaten 2X by Gene Tunney and dropped as well by Gene who was not quite the puncher as Walcott and Moore nor the pin-point puncher with known finesse. Gene was a mover and boxer but not in the class of JJW, Moore or Ezzard as a puncher Firpo landed one of of desperation as Jack was going in for the kill while Marciano loved it when you came to him. I also seen Jack get caught nice and staggered by the small but rugged Carpentier so I would suggest you look again at who was easy to hit.