Atlas Shrugged was not “about” the thirties. It’s genius is that it is about every generation since then, becoming more and more pertinent as time goes by. Look around. Whats happening now was described in great detail in the book.
I agree there is a timelessness to the ideas, as is usually the case with literature. But the world in which those ideas were presented was one that in many ways seemed “past” when the book was published.