I gotta say your generalisations of the democratic party here are so wildly over the top, that it makes me not want to engage with you at all. Having different wings of a political party is normal in most democratic political systems and not necessarily a bad thing, as long as they can work together on the important matters. You don't need to burn something down because you don't agree with everything they stand for. And yes I do agree there are bad people in the party and people that have simply been there too long and are not fighting like they should. But that doesn't mean the whole platform should change.
What you want will both give republicans free reign to do whatever they want while the Democrats fight amount themselves and make sure the party doesn't actually have a fighting chance of standing up to republicans in elections.
You need moderates to win, this has been true for years and is even more so now that the republican base is getting more and more radicalised. You are never convincing any of those people, so you need to convince people on the fence to go out and vote against them. A highly progressive platform will simply not be able to actual win big elections, 100+ years of American culture and a generally broken system have made sure of that. The only way to get there is slow and steady strides and sticking together against a common enemy.
In my mind what actually needs to happen is that the whole system, constitution and all, gets thrown away and built up again, but that probably can't happen without a literal war, so this is the best option. Democrats fighting among themselves while their country turns into a prototype fascist state is one of the worst.