Uh, Holmes took the "title" of a 35 year old guy who had it handed to him in a boardroom. One of his best defenses was against 35 year old Shavers as well, and let's not forget Ali. As for blown-up LHW, he LOST to a blown up LHW. Apart from that, he failed to meet most of the other best guys of the era, who were mostly drug addicts and fat guys. The 50's never had a "champion" like Pinklon Thomas who gave interviews and possibly even fought when on heroin. The 50's was not that bad, and at least the best met each other.
The fighters, while inconsistent, were talented. Dokes, Witherspoon, Thomas, Tucker, Douglas, Bonecrusher Smith, Bruno, Tubbs and others all would be top contenders in any heavyweight era.
Marciano is ahead of Dempsey the ducker who was champion for half of the twenties and is a highly ranked heavyweight all time. Ezzard Charles, albeit blown up, would run through post Lennox Lewis heavyweight champions, akin to Usyk today.