For example, Murray Rothbard argued in America’s Great Depression (1963) that both Herbert Hoover and FDR worsened the economic downturn through interventionist policies. He believed FDR’s price and wage controls, massive public spending, and business regulations stifled economic recovery.

My point is not that the person I was replying to is definitely wrong about FDR's policies, but rather that the effects of FDR's policies are uncertain enough that the fact that FDR imposed them in the 1930s cannot credibly used to lend strong support to any argument for any economic policy to be imposed today. The post-WWII economic boom for example happened after most of FDR's policies had been repealed.

Thanks for the reference. I generally agree that, from a very high-altitude, it's difficult to know whether New Deal policies shortened the depression given that WWII shook up the US so much. However, there are many things introduced during that time that have had a visceral effect on the average American's quality of life, saved lives, and would be terrible to abandon: the FDIC, the construction of a massive amount of infrastructure, social security, etc.