Nature can't screw up because it has no purpose, no feelings, no plan. The most adaptable organisms survive (parasites, diseases). It can create monstrosities and it can create livings of incredible beauty.
If we attributed the existing living world to God than a lot of impossible questions arise:
Why would God create dinosaurs and then wipe them out? Is He not perfect? Is He not wise?
Why did He make some of the dinosaurs carnivorous before the sin of humans? Doesn't he hate violence? Is He not love?
Why do carnivorous animals and plants exist today?
Why do diseases and parasites exist?
If God created them what do they say about his personality?
This are not easy questions that's why those who believe in God often ignore them. But can we understand God if we don't understand his creation? I, myself find it impossible. If God exists, which I doubt, we can't understand Him and I don't he cares about that.
This is just his creation, not to mention his inspired Word.