Your vote is sending a signal to future elections. If Ohio has a 20-point red margin, it’s unlikely to get any attention from blue candidates. If it has a 5% margin, that changes, and suddenly the next campaign considers spending time & money to try and move the needle.
Remember the old Roman adage: “you’re not defeated until you admit defeat”. If you don’t vote: you’ve lost. If you vote, you might still lose that election but there’s a better chance to win in the future.