Thats your take, not the take of the people who go there. In your eyes, letting them die is "not caring about them" but in islam, that just means that they will get much better rewards in the hereafter.
In islam, the world is a place of test, not a place where to get justice. You get justice in the hereafter.
Hand waving to you sure, but to many believers that is the truth. You cannot say that this action is bad because you do not possess the ability, i mean think about the butterfly effect for an example why it is not possible. But Allah is infinite therefore he possesses this ability.
Secondly it is his choice, for how to exercise his love, whether in this world or the afterworld. Muslims believe that he is most loving so when we don't see it in this world the assumption is that we will get it in the hereafter.
This world is not a place for justice and neither is it fair, for we get it in the hereafter.