"From a Christian perspective, God created the world and it was perfect. Everything negative - illness, war, death, injustice - stems from humankind's rebellion against God.
(I hope this doesn't sound preachy, it's not the intention at all, but just trying to explain what I think most Christians would say they believe.)"
It wasn't perfect though, was it? He put the tree of knowledge of good and evil in it, and the serpent - and did this knowing that Eve would eat the fruit. He then had a reason to do something God is particularly partial to in the Bible: group punishment, because Eve's 'sin' meant he could curse generations of women and infants to dangerous and painful birth. Lessons learned: women, DO AS YOU'RE BLOODY TOLD! and 'EVERYTHING BAD IN THIS WORLD IS WOMEN'S FAULT!' The lesson which would underpin epic misogyny in the Church for the following two millenia.
So according to your explanation my innocent son's cancer is because of someone else's 'sin' in some sort of supernatural way, because unlike war and conflict which humans have agency over, cancer that's caused by genetic glitches has always been with us. It's part of how we were created.
"Look in from outside and what you see is a bunch of people appeasing an invisible deity who is supposedly omniscient, omnipotent and benevolent, but whose lack of intervention in his creation needs remarkable amounts of human ingenuity and intellectual gymnastics to explain." This, completely @FlaubertSyndrome Christian apologetics is squirm making.