Surely that has much more to do with artistic skill than frequency response of their ears. Having excellent hearing won't make you intrinsically skilled at audio mixing.
> Most people won’t hear good audio gear but that’s not related to age ;)
The relationship between age and hearing loss is incontrovertible. Hearing loss is cumulative, it increases with age. Some people lose their hearing faster or younger than others for a wide array of reasons, but nobody is completely immune to it.
Anyway, no need to believe me, just go and do a test and see how well you can still hear and you'll come away even more impressed with your brain than with your ears. Your ears degrade and your brain works very hard to make up for that degradation.
Composing and directing music are two very different activities. I'd expect the first one to work way better than the latter given strong deafness. I don't know about a successful deaf conductor in the modern times.
Yet I think we are agreeing in the core - hearing music is more than just ears, it is also perception, which is why some people get wrong ideas about and if something sounds better (see the original topic here). Yet that does not mean there is not better gear than other and that no one can hear the difference between anything. Actually better hifi gear will sound better, even to older people.
Good equipment will often sound better, to what amount is the question. And yes some things are just fake and don’t deliver better sound, so listening yourself is very important.