FDR was a moderate, organized labor forced him to make concessions to the working class. FDR got credit for 40 years of labor organizing. Everybody knows about the new deal in 1935, nobody knows about the 1934 nationwide strike wave.
Granted, was he terrible? In some ways yes. Japanese internment was a particularly egregious example. Tbf, Abraham Lincoln was also a moderate re: slavery until historic conditions forced the issue of emancipation. A bad president would have held the line against objective historical conditions and deepened the crisis. This is what Trump does. FDR wasn't a bad president like Trump, but IMO he was more like a guy who did the minimum when wealth inequality and crisis was not just the worst, but when the organized workers demanded change and were able to fairly quickly take over whole cities and industries in order to force our demands.