If anything the great depression supported this thesis of stocks always going up, and you can safely forget sweating the actual underlying economics. If you held through the crash or bought at the bottom you'd obviously be doing fine. Look at this chart (1). Seem familiar? Looks a lot like the great recession or March 2020 to me: a big plunge that took headlines followed by an unstoppable bull trend, in this case one that kept advancing for decades and decades to today (2).
Keep in mind what is key with this thesis is not some fantastical belief that stocks always go up out of magic. It's the understanding that the actions undertaken by the federal government and major banks that run the global economy will always generate increasing stock prices no matter any local blip or bloop or crash or fall in that moment. Buy the dip and take advantage of the sale price, then enjoy the guaranteed ride upwards supported by every major financial institution and first world government on earth, is what the past 100 years of macroeconomics have taught us.
1. https://static.seekingalpha.com/uploads/2011/8/4/763684-1312...
2. https://static.seekingalpha.com/uploads/2020/3/16/saupload_b...
