Vote for the change you want to see.
The Republican party got remade because trumpists showed up and outvoted the party elites. No reason it can’t happen for the Left except for laziness and apathy.
If all the progressives furious about the state of affairs now had shown up for Sanders in 2016, I doubt we’d be in this hellish timeline. Sadly, he needed the young progressive vote to show up.
As a leftist who’s been voting in Democratic primaries for the last 24 years: Outside of some extreme enclaves in major cities there aren’t enough of us to make a difference that way.