FDR was a pragmatic Progressive and didn’t enter the White House with a bold agenda for dealing with the Great Depression. He had ideas but nothing big and bold. In airplane pilot’s lingo “He created the New Deal by the seat of his pants.” Saying that the Roosevelt Administration made it up as they went along is probably too loose but they put in ideas as they got them. They had not developed a New Deal agenda as far back as the 1932 presidential campaign.
The Socialists were calling for steep new taxes on the wealthy. I’m sure they wouldn’t have left what was left of the middle class off the hook. They called for nationalization of industries and creation of a Nordic-like welfare state. The Libertarians were saying that government should stay out of the way and let the economy fix itself, if anything lower taxes and regulations on private capital.
FDR’s New Deal was in the middle. It affirmed American capitalism as a good system that empowers millions of Americans to be successful. What it lacked, and what the New Deal provided, was an insurance system, paid for by the economy itself, for people who need help when the system failed. This is how Social Security, Unemployment Insurance and Welfare Insurance were created. The New Deal, included, as well, new infrastructure investment to do needed work that the private sector was neglecting and to provide employment to millions of Americans.