If he's saying "everything is worse now that buildings don't look like the Taj Mahal, and clothes don't look like traditional Chinese ceremonial robes", how does this translate into support for Western exceptionalism?

It seems to me like your postive example is a non-sequiter. I don't think Scott is arguing that it's impossible to make architecture that "moves the spirit" using modern design/construction. He's arguing that, for the vast majority of modern buildings, nobody is even trying to move the spirit. Even in cases where historically we would expect them to (major institutions, public art installations, large companies, rich people with large houses).

The question is, why do people with almost unlimited resources choose to build rectangular prisms of largely unadorned glass or concrete?

And your answer is (please correct me if I'm wrong), because modernists think it's better, and people generally agree even though they can't express this agreement in surveys?

What is your basis for believing this? And even if you engage with the literature on aesthetics in architecture, how do you find yourself siding with the modernists instead of the critics of modernism like Christopher Alexander and Nikos Salingaros? This is a serious question, I've been trying for a while to find a defense of modernist architecture that I can actually understand.