At the risk of offering up yet another of those tortured metaphors, let me proffer my own architect analogy: an architect is not like a construction architect, but more like the conductor of a band or symphony. Yes, the band could play without him, but at the end of the day, the band plays better with one guy coordinating the whole thing. The larger the band, the more necessary a conductor becomes. Sometimes the conductor is the same thing as the composer (and perhaps that's the most accurate analogous way to view this), in which case it's his “vision” of how the music in his head should come out in real life, and his job is to lead the performers into contributing towards that vision. Each performer has their own skills, freedom to interpret, and so on, but within the larger vision of the work.
Is it a perfect analogy? Heavens, no. It falls apart, just as every other analogy does, if you stress it too hard. But it captures the essence of art and rigor that I think seeing it as “architecture” along the lines of civil engineering just can't. At least, not easily.