The problem is that the broader Democratic electorate is a much bigger tent, with overall much more moderate politics, than online leftists are typically willing to admit. We're still only eight years past an election where Hillary Clinton took the Rust Belt for granted, and we all paid the price for that when traditionally solid union votes swung to Trump because he was boosting fossil fuel extraction while Clinton implicitly threatened the livelihoods of families dependent on coal and fracking jobs.

Healthcare you have a point on, but also keep in mind that the last time Dems had the votes for sort of sweeping reform was 2008, and what we got out of that was the ACA, which for all its faults was still a big step up over the status quo. Obama was going for a big bipartisan win, in spite of McConnell's announcing that he was killing bipartisanship in the GOP caucus, and that was a mistake, but perhaps an understandable one given that up to that point that's how Congress had always worked.

There have been windows of time since in which Dems have held the Presidency and both houses of Congress, but never with enough margin to defeat a Senate filibuster, and with DINOs like Manchin and Sinema standing in the way of filibuster reform. I do not doubt that progressives in Congress would move an M4A or public option bill through the legislature if, in 2025, the House flips back and the Senate stays Democratic in spite of the unfavorable cycle, but withholding your vote doesn't get you any closer to that happening.