The necessity of voting, from a moral standpoint, has been around as long as the US govt. Such necessity has grown in recent decades as more and more openly immoral politicians decide to run. I’ve heard many sermons from priests who say it is a mortal sin to abstain from voting where morals (ie abortion) are involved, especially when the contest is close and contested.
Now, your point that there are more effective means of fighting abortion than voting is true, but the requirement to vote is not diminished.
In the case of abortion, we cannot look at the overturning of Roe v Wade as the ONLY goal. The election of national AND STATE politicians is very important and many states have passed VERY good laws limiting abortion. Even if such laws are partially overturned by the Supreme Court, God will bless the state and country for these moral victories because He will recognize the fight for Truth and Life.
So don’t give up on voting. Our country is not lost yet! With prayer and fasting, miracles can be accomplished.