Who is to define progress in a UTOPIA?

 When I look back at the quotes of Tafuri I wonder to myself (and I could be wrong) but how can someone go on to talk of how the ideas of utopia are gone, and that modern architecture has lost the "purity". He looks back to old renaissance ways of thinking to cloud his views on the development and growth of architecture that have come with the modern movement. I think especially about his criticism of James Sterling. The way Tafuri writes he knows that the "perfect" way of architecture is gone but cant truly say why makes me pose the question of the title... Who is to define progress in a utopia?