The OP presents a series of impossible choices: don't vote and make the world worse or vote for the system which makes the world worse. Both choices make the world worse despite seeming to be completely opposite. How does this occur? It's obvious enough that there is a rupture between the individual choice (vote/don't vote) and the aggregate effect (make the world worse). But what is the mechanism by which one becomes the other? On the surface, the world is nothing but an aggregation of individual choices. Humans made society and they made capitalism so why is it so hard to destroy? Scientific Marxism is the uncovering of the laws of the structure itself, in this case capitalism/voting which lead to outcomes that arise out of the actions that form them but are independent of them. But Marxism goes even further: the subjects of the structure are actually produced by the structure rather than the other way around. Voters are not a type of person that created the American government but actually the system of American governmentality, formed through the violent creation of the United States to the present, forms voters in its own image. In thinking in terms of "voters" as a unit of politics you've already lost. The same can be said philosophically of the individual as such, a category Marx abolished with the invention of abstract labor.

Liberalism on the other hand is two related fantasies: first, that individuals are equal and autonomous and therefore aggregate outcomes are merely the average of identical units. Thus the idea that politics is a matter of convincing others, adding more people, and "shifting" the average towards liberalism. Despite its theoretical pretensions, this is why neoclassical economics never goes beyond simple algebra. It's even possible to imagine shifting to socialism given that people are already socialist by nature, this simply has to be awakened. (Chomsky's hypothesis)

Given the opposite has happened for 40 years a second fantasy has been added to rescue the first: a conspiracy of unreasonable people warps the average. This is the realm of Russia conspiracy and the "deplorables" of course but it is actually logically necessary to liberalism in decay and equally applies to seemingly reasonable or even socialist judgements about right wing racism or capitalist control of the media (the question is not whether these occur or not but what their structural causes and effects are). Marxism opens a truly terrifying possibility: even if every single person voted or acted in a different way, this could have no structural effects at all. Marxism fully breaks not only with liberalism and anarchism but also syndicalism and economism with Lenin and asserts the autonomy of the conjecture, or the primacy of class struggle and socialism as a political struggle within and through the contradiction of a structural formation. I think people know in their hearts that even if everyone voted for Bernie Sanders this would have no effect at all, I mean this literally happened in Greece and is happening right now in Mexico, but they are trapped in liberalism and cannot overcome the rupture between singular and structural except through increasingly bitter conspiracy, often confused with socialism.