The Democratic Party does not care about winning elections. They care about maintaining the ruling class political establishment from which they directly benefit.

they're prepared to have a small % of social democratic politicians in their ranks whose ideas will never be practical against the conservative supermajority (Republicans and most Democrats) of politicians. This is not a system that can be reformed to serve the working class

we have hundreds of years to show that losing does not disrupt the hegemony of the Democratic Party. Nothing is at stake for them so long as the overall existing order of the US is maintained.