I think people rightly don't believe it because it's apparent that the economic machine in the United States is not built for the benefit of the average worker, it's built for the benefit of the capitalist class that's captured the government. Republicans may be more up front about upholding the status quo, but there are plenty of corporate Democrats that will support the same status quo while chasing the social capital that comes with agitating for change that more progressive groups are pushing for.
People don't have faith when they're constantly sacrificed at the altar of "the economy" without seeing any of the benefits of an improving economy. For a good example, look at how the BNSF rail strikes were resolved before Christmas last year. Rail workers were striking for very reasonable things like 7 days of sick leave per year (up from literally 0, per the contract they had with BNSF) and appropriate staffing to prevent emergencies (like what happened in East Palestine, Ohio in early 2023), and what did Biden do? Biden, the guy who campaigned as one of the most pro-labor and pro-union presidents in recent history, stabbed them in the fucking back and made it illegal to strike because an unstable supply chain around Christmas spelled "economic catastrophe". Biden would rather go to bat for a large corporation than for the workers that corporation is shamelessly exploiting.
Zero difference. They're both the same shade of conservative, far-right, religious fundamentalist.