Here's a little middle school social studies lesson for you: there is a lot more to the government than the President.
Bernie Sanders could be sitting in the Oval Office right now and he'd still be struggling with the political realities that Biden is dealing with today. There would still be multiple wars raging, there would still be Republican obstructionism, there would still be a Republican controlled House and a tied Senate, etc. And I'm willing to bet you would be sitting here commenting on how "disappointing" he ended up being as a progressive....
If you want big, sweeping FDR-style changes, then elect a big sweeping congressional supermajority like FDR had. It's not rocket science, people like you would rather just shy away from the political reality of getting bills passed in favor of complaining online, and it's getting boring.