People who rate Ali as the GOAT aren't idiots. He had the perfect blend of speed and skills that could have beaten any other HW. The same applies to Lennox. Both guys would have had a real shot at beating any HW in history when they were on their A game.
It works both ways. Joshua's never seen anyone like Mike. How do we know he has more heart? How do you know Joshua wouldn't have been intimidated?
It doesn't always play out like that. There's techniques that aren't as common today, and fighters were more active back in the day, and they encountered every different style on the way up.
To claim Joshua or any other active HW(maybe except Wlad) is a far superior boxer to prime George Foreman is a moronic statement of the highest order.
You focus only on America. The sport has a much bigger talent pool now with European and African talent coming in. The reason why Europeans are dominating is because Europe always produced better athletes than America and now when boxing has become an interesting and valid option for European athletes Europeans have started to dominate, just like they dominate every relevant global sport (football, tennis, formula one).
Fighters were too active fighting bums back in the day. No one is stopping modern fighters to fight more and no one is stopping them to try out all kinds of techniques. They reason why they don't do it is because it doesn't work anymore because the sport improved and there are new techniques that are more important.
Not all of those old opponents were cans, and their losses were deceptive. People lost a lot back then because they fought so often against other good opponents. Sparring does not replicate a real fight, encountering different styles. A fighter today can have a prolonged career, but it doesn't mean he's going to have learnt as much. Kovalev and Ward can only study their 36 min fight. Ray studied Jake up close, 6 times.
He had decent power, but Deontay's technique is very poor. He can't blast everybody out. When he can't use his right hand as his safety net, what's going to happen?