it is a historical fact that most of the best mathematicians make their famous discoveries when they are younger than 30. if you have studied the subject, you'd know this, so i assume you just dislike these facts and argue for the sake of it.
Maybe people in their 60s were not at the center of research, but I would say that the field was dominated by people in their 40s (certainly not by 20-something).
I cited the Fields medal, because their artificial limitation on age is one of the first things that comes to mind when talking about the subject