It's much easier to make a bill that says "we cut research funding to tax billionaires less" and get your cult members to vote for it than it is to make a comprehensive healthcare bill without loopholes that may have to rework an entire industry, while having a thin majority.
From the 117th congress wiki:
Despite Democrats holding thin majorities in both chambers during a period of intense political polarization, the 117th Congress oversaw the passage of numerous significant bills,[3][4] including the Inflation Reduction Act, American Rescue Plan Act, Infrastructure Investment and Jobs Act, Postal Service Reform Act, Bipartisan Safer Communities Act, CHIPS and Science Act, Honoring Our PACT Act, Electoral Count Reform and Presidential Transition Improvement Act, and Respect for Marriage Act.[4]
Do-nothing democrats is a lie spread by conservative media, their job is just significantly harder, and they don't have a propagandized cult behind them.