Norton has two fatal fundamental flaws against punchers- he freezes, and he'd back up in straight lines. If you want to believe that only historical level punchers brought that out in him, hey, it's your fantasy. Go nuts. But when a guy goes 54 rounds with Ali and Holmes in 4 fights, and lasts 12 rounds combined against the 4 best punchers he fought (nearly much less- a 20 pound Garcia nearly had him out in the 1st, which wouldve meant less than 5 combined rounds covering 4 KO losses), that's a glaring stylistic weakness on a fundamental level. I certainly wouldn't have put a nickel on him against Frazier, Bonavena, Lyle, or most punchers since then. He was a quality fighter when his chin could handle it, but that doesn't make it good. Arguing that his chin was actually pretty good is a non-conformist hipster doofus argument that's reached the end of its useful shelf life.
Norton didn't have a good chin. While his engaging style was very entertaining, it also put him in harms way. So he didn't match up well vs. aggressive punchers Foreman and Shavers. Few hit as hard as those two. In his other fights, Norton's chin was fine vs the solid type of hitters. If he was in his prime today, Norton could be the best of the lot. I'd pick him over Wilder, a 40-year-old Wlad, and Fury. Need to see more of Joshua.
Norton was known as being chinny on the west coast. One persistent rumor was that Quarry knocked him out cold during a sparring session in the early 70's.