Let's assume for a moment that what you're saying is true. I'll "steelman" you're argument. Let's assume that the criticism of Harris "from the left" played a large enough role for enough people to stay home.
What you are advocating for is that if a political campaign is bad, but "less bad" than the alternative, we should not criticize it. We should not demand the candidate for our party run on policy positions that we want.
You realize you are advocating for an increasingly worse and worse political choice over time. If no concessions are ever offered by politicians to their voters, and those voters still show up religiously, that is not democracy. That is a cult.
Not only that. But what you're advocating for is impossible. You will never live in a world in which people don't criticize a candidate that is "less bad" than the other candidate. You can, however, live in a world where the politicians that lose elections to historically unpopular candidates like Trump, are replaced by candidates that actually offer policies the voters of their party WANT. We are seeing this grow with DSA right now.
So, even if what you are saying was true, the solution would not be to shame voters. That literally will cause MORE of them to sit on the couch on election day. That's just people. You can't sustain a political party by being "less bad" than the alternative. People will stop showing up. People sitting on the couch when their politicians ignore their material needs is literally how democracy should work.
You're saying the same thing I am saying. But you're for some reason placing blame on potential voters doing exactly what they SHOULD do in a healthy democracy. You seem to want a party that has cult like loyalty as long as "the other guy is worse". Well, that's exactly how you get worse and worse political policy, constantly shifting rightward, for decades.