The problem is that there isn’t a left to vote for, you either vote for right or far-right. That’s why the ratchet effect exists, both parties are right wing, just separated in how extreme they are, with the Reps being overt fascists.
Actual leftist change is not going to come from voting for liberals. Absolutely vote for Biden if you wish, this isn’t an argument against voting for him. However, if you think voting for a right winger will shift the overton window to the left, you don’t understand the nuances of the overton window.
Actual leftist change comes from direct action and organizing. Strikes, mutual aid, canvassing, raising class awareness, spreading leftist theory, protesting, actual outside pressure is what changes the overton window.