Do absent users blindside architects?

A visionary edifice, a revolutionary feat of engineering, a blot on the landscape, a brutalist carbuncle. Rarely does architecture lead to subtle superlatives. But, sometimes architects design with only a vague notion of the users of their constructions. In the absence of personal profiles of the people that will swing through those grand front doors and ride the escalator to the giddy heights of the top floor, what guides an architect in planning their stucco stairwells, their fantastical fenestrations, and their vaulted visions?