Voting is good, I recommend doing so. Especially for local elections - state and municipal officials are extra important right now.
But you are not at fault for the outcomes of elections. A candidate is responsible for earning votes.
One vote doesn't mean much, which is why you should never vote alone. With minimal effort, you can double, triple, even multiply your vote by 10 by getting other people to the polls.
Voting isn't a private act. It's an act of solidarity and it is intrinsically social.
Definitely get out and vote! Get friends to vote! Don't tell them they're at fault for voting wrong if the obvious choice candidate can't draw enough delegates to win in a gerrymandered system.