Perhaps that is the way you should be thinking, Rebekah - what is there about a store that would make us more likely to shop there, at 65+ or any other age.
I would say -
Assistants who are more than a size 8, and older than 21.
No loud jarring music. If you must have music, have it quiet and soothing.
Attractive clothes that are neither frumpish and "elderly" nor outlandishly "fashionable", ie hideous on anyone.
Many price levels. Sometimes we want something expensive for a special occasion, sometimes a more everyday thing. You never know, if we are looking for trousers to wear round the house we might see just the thing for that wedding in two months time.
Many sizes, with the larger ones as attractive as the smaller ones. Not a rack full of sizes 10 and 12, with one each of size 14 and 16. It is normal to put on a little weight as we get older.
Many colours. Some of us like classic greys and navies. Some of us like pasteles, some like bright colours. Not many older complexions suit hard or sludgy colours.
All the coats together, all the trousers together, all the tops together, and so on. We don't like traipsing round a dozen "collections" to find two or three possibles to try on.
Individual changing rooms with plenty of space and clothes hooks, and mirrors which show our back view.
A small cafe or even a coffee/tea machine.
Comfortable seats and a newspaper or two for our other halves to sit and wait for us to emerge.