Is it true the Aztecs didn't get anything, though? A religion sacrificing people is a show of power likely to keep any common citizens rebelling against the priesthood. In modern times we have police kneeling on the necks of people until they die from lack of air. Both are just a means to kill powerless people to keep the powerful people in power. Our modern rulers put non-religious names on things, like "The War on Drugs", but it's the same thing.