I don't think he means it's no use. Most large public sculptures express some historical/heroic/national/regional idea, often a figure we're meant to admire. His work does not do this - it's not a historic figure, but a vast anonymous figure, so people might respond in different ways. What is the huge faceless angel doing there? Its purpose is less clear than a statue of a national hero that is meant to reassure us about our ability to resist threats, etc.
It says here that one aim is to serve as a focus for our evolving hopes and fears.