/lit/ - Literature

Why is it that most thinkers prior to World War 2 were deeply pessimistic and insightful about the perils of modernity but after the war most people celebrated the modern era?

Having finally read Spengler, what are the main arguments against DoW? I would expect some to argue that cultures aren't really biological organisms but you could interpret that aspect of the book as being a mere metaphor and not a literal organism. Is there anything else?