One of the most disappointing things about the past three years has been seeing just how weak and spineless much of the Democratic Party has become. It's not really a surprise from Republicans, as they've been building up to Trump for decades, ever since at least the Southern Strategy was implemented, and Trump is arguably the final expression of their political evolution (or devolution) since the Nixon years. Also, it's obvious that most Republican pols are terrified of getting primaried by Trump's base, or having Trump and his base turn against them. Not that it makes it OK, of course, but it's not really a surprise.
Democrats, however, have no such excuses. I've become convinced that many veteran Dems (like Schumer) are living in the past, and still trying to pretend as if it's the 80s, when you could cut deals with moderate Republicans like a Howard Baker or Bob Dole and get things done. They simply don't know how to operate against guys like McConnell or Trump, and seem intimidated by them. Also, I think it's clear that many Democrats (especially older centrists) are just as frightened of Trump, his rural base, and right-wing news media as Republicans are. They seem to be paralyzed by fears that if they try to impeach Trump, or even just act more forcefully against what Trump, his administration, and other Republicans are doing, then they'll be called out on Fox or the rubes will come after them. They're acting as frightened as most Republicans are. It seems to be no accident that most of the congressional Dems who are really standing up to Trump are the younger members. The Dem presidential candidates seem more willing to call out Trump, but even there is a clear fault line, with Biden seeming to think that if Trump is defeated, maybe the GOP will return to "normal", whatever that means.