The question is about Rocky in the 1970s. Nobody is saying Rocky can't compete. Leon Spinks was champ in the 1970s. With a three year peak timed at the right time at any particular point if the decade Rocky is good enough to be a champion for sure. Obviously some points in the decade he stands more chance, others less so. Any more than three prime years Rocky burns out and declines several levels. He's not superman. Still, it's not outrageous to expect Rocky at his best to beat any one Foreman beats in the 1970s and anyone Frazier beats in the 1970s. Any version of any specimen Spinks beat in the 1970s too. That's most of the champions. Foreman at his best is not a good fight for Rocky ... but darn that young George was one green unproven contender if ever there was one! Heow he got rated so highly and past Frazier and Ken Norton ...but Ali had too many tricks and resistance for him. Foreman pace was not elite level. You cant rule Rocky less than 50-50 just on a punchers chance, but he has stamina and seasoning on George too. Sure he has size and power so it evens things up. But it's a pick em since George was never a finished article in the 70s'.
I didn't give a toss about those teachers then, and don't now. They were only bullies, hitting kids with sticks and throwing black board rubbers at them. But I digress. Foreman might well be easy to hit with right hands, and yes he could be out boxed, like he was by Young. The chances of Marciano out boxing him are less than zero. The problem with the guys you mention is they all ( with the exception of Lewis ) need to get close to George to do their damage with the right hand, and as Lyle, and almost everyone else apart from Ali found out to their detriment that was far from easy, and had devastating consequences.