The point being you're wrong. A 43 year who is ranked P4P number four in a particular generation of fighters is exactly as good as a 28 year old ranked P4P number four in that same generation. Because nobody handicaps their ratings by age, it's a simple measure of how good you are.
Can i point out Hopkins was p4p number 3 as of the time of the fight. I believe it was Mayweather, Pacquiao, Hopkins, Calzaghe, JMM However - otherwise, you're right on the button...
No, a win over someone who was ranked as one of the best four fighters in the world at any weight at the time is a career defining moment. How old that person is is utterly irrelevant. 23, 33, 43, 53.
Not many people think that the Hopkins that beat Council and Brown was better than the version that beat Trinidad. Interesting.