> The only way to square this away is to assume that god isn't unwilling to intervene, but is unable to.

Or maybe it is unwilling to intervene because he is immensely powerful but not omniscient. And so, if he wants to create the perfect world, he has to run tests first. The same way we break materials to know their physical properties, that god is breaking humans to test their limits, so that the next iteration will be better. He is not sadistic, we are just unlucky to be in the cancer test batch.