But Joe Louis also lost to Rocky Marciano at the end of his career, yet was unable to revenge that loss. Which is exactly my point; when you're young you can avenge losses, because you're still at your prime (or even coming into it). When you're old, every year makes you worse. Young folks don't get this, at least until they get older themselves. At a certain point there's no chance of bettering your previous results, all you're trying to do is slow the decline.
And in high level sports that can happen fairly young. Usain Bolt lost to two guys in the 2017 world champions with what for him is a bad time, and at age 31. Old guys like me will nod and say he's losing a step. Young guys will say he should be as fast as 30 as he ever was, and losing just proves he was never as good as the two guys who beat him - ie that Usain Bolt was exposed, and there's no way he can be considered the greatest sprinter, since he'll never avenge those losses (he retired because, as he said, at 31 he couldn't run like he did at his prime). Age isn't just a number.
People age differently. Again, every older person knows this. I'm retired. Some of my retired friends, who were better athletes than I was when we were all young, are now much worse athletes. (Sadly some are even dead - its hard when friends start dying). Does that show that they were never better than me, or just that I aged better? As much as I'd like to say my being able to outrun them now (some of them can barely walk) means I was always faster than them, aging simply doesn't work that way.