You dont get those changes by just blindly voting against the Republicans. You have to actually pressure your candidates into supporting what you want. Companies and lobbiests are able to do this with giant sacks of cash. Normal people do it by protesting and making demands of their officials to force a response. Showing nothing but contempt for anti-war protests is always a bad look for a president running for reelection.
Biden has all the leverage on Israel to make them stop the killing. He can threaten to pull military aid, send in US forces to distribute humanitarian aid, or put sanctions on Israel. All of those would stop the killing, making people angry at the US response willing to vote for Biden, paving a path for his re-election. Why are you so against him forcing Israel to stop the genocide if it is his only path to victory?