Let's List FDR's failure:
1) Failure to unite the country in a time of war (see Thomas Fleming "New Dealers War")
2) Appointment of Communists to high positions
3) Appeasement of Stalin.
4) Refusal to plan for the postwar world
5) Hostility to the British Empire
6) Failure to build up the US Air Corps and Navy prior to June 1940.
7) Failure to plan for the German U-boat attack in 1942. Refused Navy advise to build DE's prior to Pearl Harbor.
8) Failure to adequately provide for the defense of Pearl Harbor.
9) Policy of Unconditional Surrender
10) Endorsement of the Morganthau plan.
11) Failure to build Aircraft Carriers instead of Battleships prior to 12-7-1941.
12) Endorses Marshall's absurd "Sledgehammer" plan.
13) Refuses to negotiate with Mussolini or Italian Military prior to July 1943.
14) Refuses to delay start of Pacific War by compromising with the Japanese. We could have delayed the start of the war by 3-6 months which would have given us time to prepare for the attack.