God would be quite unfair to save anyone.

Our intuition that God should save all people rather than just some is based in our false but natural feeling that all people deserve saving. Even after we are converted and know better, we still tend to think of people as basically good when of course they are the opposite. But once we look at human beings from God’s perspective instead of our own, we realize that he ought to punish us all in hell forever. He ought not let a single one of us into heaven. That’s why it’s called the “gospel of grace”: grace is undeserved favor.

In other words, not a single person ever has any claim whatsoever on God’s salvation. If God decides to give it to some people, he is being gratuitously kind to them. He is not giving them what they deserve. Commensurately, his failing to be gratuitously kind to other people is not a defect or imperfection on his part. He has utterly no obligation to those he didn’t pick for salvation—because they have utterly no basis to expect his favor. He is not unfair to give them what they deserve—hell—he is, in fact, perfectly fair.