Congratulations -- we did learn a few things from the 1930s! Just not enough things. As you can see in the chart below from Justin Fox, job losses during the Great Depression dwarfed those during our Great Recession, but job gains have been much slower this time around.
Our weak recovery has put us halfway to a lost decade -- and if it continues, our slump could, as Brad DeLong points out, end up being as costly as the 1930s slump. Now, this wasn't supposed to happen. We, or at least Ben Bernanke, were supposed to have studied and learned from history. And we did. Bernanke has been determined not to let the banks fail or prices fall like the Fed did in the 1930s. Back then, the still-new Fed watched as bank runs turned a recession into a depression -- and then into a depression that snatched the "Great" modifier from the 1890s depression. As Irving Fisher explained, debt and deflation fed on themselves in a cycle of mass bankruptcy and unemployment: Financial panic pushed down prices, which pushed down wages, which made it harder to pay back debts, which led to more defaults, which led to even more panic, and so on, and so on.
But this time around the government stopped the vicious circle. First, Congress bailed out the banks. Then it put money in people's pockets with the stimulus. And, meanwhile, the Fed threw money at the economy every way it could: it lent against almost any collateral, cut interest rates to zero (and then promised to keep them there), and bought long-term bonds. This collective wall of money has been enough to prevent a 1930s-style collapse, but not jumpstart much of a recovery. Just look at how flat the blue line has been above.