You could have 100 Feinsteins and 435 Pelosis and never make progress to the left because they're not interested in doing anything but preserving their own status and power even at the expense of their constituents.
When Republicans are in power they are extremely aggressive about cementing their future ability to regain and maintain that power and they do it with single minded focus.
Voting is not going to fix the DNC.
The DNC has repeatedly told young people to go fuck themselves so you can't be surprised when they don't turn out to vote for some crusty old man who is going to preserve the status quo (which already sucks)
Like maybe we would be in a different spot if Obama had aggressively used his opportunity to close gitmo and enshrine federal abortion protections and pack the court, but he didn't, so here we are.
We have one regressive party and one status quo party and the regressive party wants more than anything to suppress the right to vote so please don't pretend that this is unexpected or surprising.
It is fixable, but the people in power don't want it fixed, so we have to make them fix it.
If that means prinarying basically every sitting democrat then we should do that.