Nature is not cruel, don't anthropomorphize it. Nature has no free will or emotions or intelligence. It is indeed uncaring, because it doesn't have the capacity to care. Nature is neither good nor bad. It just is.

Whether or not it is moral or ethical to eat animals is an arbitrary decision made by emotional beings. There is no right or wrong there, only what people feel.

Someone who is vegetarian or vegan for moral reasons is making a choice, not living some sort of universal truth. Someone who eats meat is also making a choice.

Someone who eats meat but criticizes others for eating the "wrong" kind of meat is a hypocrite.

Certainly the way we farm animals for food can be sustainable or unsustainable. I wish people would focus more on that aspect than pointing fingers and making it a moral issue.