Age has absolutely nothing to do with how you dress. Just buy clothes you like anywhere. As for the GN section on clothes for the over 50s....... I do not think it has been changed since first posted at least 5 years ago and I think the clothes they show are, quite frankly, horrible, I wouldn't be seen dead in them - at any age.
I am 80, I have no problem buying clothes at any mainstream clothing retailer, although i do find M&S a bit mumsy. and safe.
I think the problem is that the OP cannot find the kind of clothes she like wearing in the shops or online and assumes it is an age thing.
It would probably be easier if she could tell us the kind of clothes she is looking for and then we can point her to sites that have that style of clothing.