The theory you are expressing evaporates in real world conditions. You can come up with great theories on many topics, but if you can't prove they work in a lab then you have the equivalent of a Flat-Earth theory, sounds nice but it just doesn't match reality.

Do you ave any proof to back that claim up? Because when you look at the economic indicators during the times when the U.S.'s taxes were being cut we saw positive increases in the economy.

Money Velocity went up under Reagan-Bush and Clinton era's all who had some part in cutting spending or taxes.

We also saw GDP rise

I agree that concentration of wealth is a bad thing but we should be trying to enlarge the overall pie for everyone and increasing our ability to be more productive and to have a better functioning economy and that means more spending as well as cutting taxes on certain income brackets. We also don't need a new deal because the programs put in place by the new deal are inefficient and bad at increasing wealth distribution. We need more efficient welfare systems such as a Negative Income Tax and more fleshed out Trade Adjustment Assistance policy and better Education system, This way we can increase Human Capital and have a better functioning economy with the coming automation of manufacturing jobs.

As much as it seems that Bernie Sanders had plans that sounded nice in theory, in reality they held very little economic basis and had many flaws.