Let us give thanks to America’s ultra-rich from a bygone era. Without them, our world would be poorer in beauty.That sounds like I’m making a joke, doesn’t it? The received opinion in America today is that the ultra-wealthy are slavering predators bent on “capitalisming” poor Gen Z coffee shop employees into penury.That’s one of the best parts about the Shelburne Museum — very little is behind velvet ropes.Well, I’m not joking, and the received …