I agree that people can try too hard to be uncool as well as cool. It's what makes the words redundant (although they are meaningful because so much revolves around them, and not just for teenagers) - whatever you try to be, you must think it's cool or you wouldn't try. Therefore I don't think we should ever criticise people for wanting to be cool, but we can definitely criticise people for having bad taste in their choice of what to see as cool, or for trying to be what other people say is cool rather than what they individually aspire to.