I've said this before, but I think it needs to be repeated:
The populist, anti-elitist lane on the left is wide open. I don't know that a mainstream "Democratic" party can take that lane, and I don't know if we should bother trying to drag them there. However, what I can say is that there is going to be some significant hay to make in that field.
I think Pramila Jayapal, Ayanna Pressley, Rashida Tlaib, Ilhan Omar, Delia Ramirez, Jamaal Bowman, Summer Lee, Cori Bush, Katie Porter, anyone who has been rat-fucked by Democrats should all abandon their identification with the Democratic party and become independents. And in the time that he has left, at their lead, should be Bernie Sanders, who never needed to be told about the consequences of running with milquetoast policies.
Even if they caucus with Democrats, true progressives need to show them that their votes aren't a given, and if they want them, they need to take a step towards their legislative priorities. Giving up our votes without leverage, giving in to the Washington groupthink: THIS LOSES ELECTIONS!
We shouldn't focus on redeeming the Democratic party. Let them sink. Focus on getting good quality, reliable progressive populists elected. The Democratic party is a fucking anchor and we're better off without it. Let those unwilling to let go of that Washington groupthink sink with it.
While this strategy may feel good, it makes the minorities Republicans want to hurt the cost of doing business. Even if Democrats can't deliver on anything substantial in the short term voting for them in elections is useful.
First, it reduces the harm done to minorities. Second, it demonstrates there is a progressive voter block the democrats could shift closer to. Third, assuming we get more elections and the Democrats aren't all in jail, it creates time for a progressive, like the Democrats your argument listed, to co-opt the Democratic Party. Like what Trump did to the Republicans and Bernie tried to do to the Democrats.
Rather than trying to achieve moral victory over Democrats, let's leverage power for the people Republicans want to hurt.