Is being brand conscious the only way to be fashionable?

No, and it often goes the opposite direction. All too often, people think the logo is what makes something fashionable, when the logo itself adds nothing in terms of fashion. However, big brands become big for a reason. But byt he time most brands go "mainstream," it is after the original designer has sold it off to a major corporation, and then the talent that made the brand fashionable is gone.