And there have been multiple successful leftist political victories. You can not get these victories without a considerable amount of leftist and left leaning voting.

The entire conclusion of the study I linked is that this is not happening.

There's nothing wrong with voting, I vote every two years, but it's dangerous to convince yourself that voting is enough. You need to also organize. You need to strike. You need to unionize your workplaces. If you really want to push the government into conceding real improvements in our lives, you need to apply direct pressure on a large scale. And when the crackdown comes, you need to collectively organize to help each other. Bail people out of jail. Help people pay rent when they're fired for trying to unionize. Doing this on a large scale is how you get actual fucking change, and it will never happen if people lie to themselves that voting alone is sufficient.