If there’s a spectrum between left and right, then there’s a point on that spectrum in the center of how the populace feels. If you have two major parties they will naturally arrange themselves immediately to the left and the right of that point. They have to in order to gather up as many undecideds as possible - they will naturally win everyone further left or further right who is not an idiot.
Voting moves this center point along the spectrum. The ratchet effect pulls to the right only because that’s the trajectory over the last few decades. If the trajectory was to the left in recent decades the inverse would be true.
Direct action and organising might also move the center point along the spectrum, but not as much as voting, and only if voting reflects the results of direct action.