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.
Just look at how basically every left party in Europe has become a neoliberal painted in a different color. Germany has a coalition of “social democrats”, a green party and liberals and they still cut welfare, try to deport black/brown people (sorely needed on the job market) and screw up climate politics.
Every concession made in favour of the left has been reached through mass movements.