Ah, words can be such tricky things because our definitions aren't shared.
When I use the term "well-dressed", I'm describing the look I saw on so many mature women in Milan and other European cities. Yes, those women were polished and well-groomed, but it was the cut, construction, and style of their clothes that caught my eye. Simple, but not simple, if you get my meaning. A belt with the patina of age, but still much more covetable than anything new in the shops. A "simple" sweater, but with a drape that looked like it was made to sit on that particular woman's shoulders for all eternity. A bag that perfectly suited the outfit and the wearer and didn't call attention to itself but was hard to forget once I saw it swinging from the owner's shoulder. Such style, but not in a way that screamed fashionista, or "off the catwalk", or even "see how cleverly I've put together this outfit". More like "this is me and this is how I dress"--regular pants, sweaters, and shoes worn by normal, 45+ women going about their daily routines. Fashionable, stylish young women--the kind whose images abound on most street blogs and who were obviously having fun with fashion--were in full display, of course, but it was these older, "well-dressed" women who fascinated me.
I still think it would be very hard to put together THIS definition of "well-dressed" from most mass market North American chains--at least from the offerings that I've seen available. Maybe it's because, as Angie says, our North American definition of style requires a good dose of current to be considered fashionable? The term "well-dressed" seemed to apply to the women I've described because they didn't seem to be as concerned with currency as their younger counterparts?