Democrats in 2020 are at risk of turning into Republicans in 2016, minus the racism.
By which I mean: emphasizing empty slogans instead of evidence-based policy, rejecting experts in favor of cranks, handwaving away questions about implementation and promising that an expensive policy will magically "pay for itself" through economic growth.
There is, in fact, vibrant, nuanced debate within the Democratic Party over policy approaches that could improve the lives of regular Americans.
There are rival proposals for how to revamp our health-care system, including through Medicare expansion, Medicaid buy-in or single-payer. Same with tax policy: Democratic presidential hopefuls have proposed expansions of the earned-income tax credit and child tax credit, a new wealth tax, tax-advantaged savings accounts for educational expenses, and so on.