That's a pretty cynical take. Much the same could be said of any industry that relies on manufacturing and marketing. I think there's value in society at large - we are social creatures and relating to each other, mimicking each other, and other forms of communication are deeply tied to how we get along as human beings. I'm not saying fashion is itself necessarily useful at large, and it certainly has the issues you described, but it's at least a byproduct of other things that are highly useful.