What I'm saying is that you seem to be judging all "old musicians" according to the tenets of hard rock, i.e., hope I die before I get old...
But there's tons of music that isn't based on youthful rebellion; and a great deal of that is made by people who have been doing what they do for more than 30 years. The statement "any band that's been touring for 30 years their eyes have dimmed and their natural forces abated" is not a universal statement, and I listed a few counterexamples.
Nothing I'm saying here has anything to do with whether there are some young performers right now who're killing it. Of course there are. But that's not the question at hand. The question at hand is, does age by itself make one a less meaningful musician? And I would answer, NO, not by itself. There are those who burned out, and all they can do is rehash their 20s. But not all musicians past 50 are like that.
For that matter most of the hard-rock musicians now have grey hair. What are we supposed to make of that? What I make of it is that it was a very limited art form to begin with, which has gotten narrower and narrrower in its appeal, and people by and large have moved on.