None of the people you mentioned ( including a whole bunch that I know, who could fit this group- my parents included) have any problems with being called “old”.. most of them, in fact, take it as a point of pride to keep doing what they do, and living how they live, despite the “old” moniker…

So, we do not need another word for “old”

what we need is a new understanding of it… or, better said, an acceptance of the fact that “old” doesn't mean “useless”