IIRC the number of people sacrificed by the Aztecs per capita was roughly the same as the number of people executed in contemporary England.
You are forgetting that the Aztecs also executed people they considered criminals etc. -- and that's in
addition to the sacrifices, which specifically used "worthy" victims, not lowly criminals. (That "worthiness", however, does not generally imply that is was voluntary, as
@CountPeter writes. Victims of human sacrifice were mostly enemy soldiers captured for that purpose. They were "worthy" because they were esteemed opponents, and the Aztecs saw it as an honour for them... but the victims evidently did
not think so. There were also in-group victims, selected for certain ceremonies, but I gather that it's unclear just how voluntary it really was, even for them. It was more likely a case of "accept your fate wth dignity, or the dishonour means your entire family gets killed or exiled".)
I keep saying this: comparing the large-scale human sacrifice of the Aztecs to atrocities in other premodern cultures doesn't generally hold water, because the Aztecs typically committed those other atrocities as well, and has the large-scale human sacrifice
to boot. Pretty much any "
tu quoque!" you can come up with (slavery, rape, ruthless punishments for criminals, extreme bloodsport where the losers get killed etc. etc.) is rather pointless, because the Aztecs did all those things
and had the human sacrifice.
Maybe, if the Romans writing about (some of) the Celts were entirely accurate, they came pretty close. But it is called into question nowadays whether those Roman accounts of mass human sacrifice in Celtic societies were not wildly exaggerated (much as the stories of Carthaginian child sacrifice were
probably Roman propaganda). Generally, we can just say that human sacrifice - as far as we know - was uniquely...
popular in some Mesoamerican societies. And since that sort of thing is generally considered pretty horrific, we can consider those societies as being relatively closest to what a real "horror story culture" would look like.
If the Aztecs had refrained from some or all other common atrocities - if they had, for instance, been morally opposed to slavery and rape and torture in a non-religious context - one might legitimately claim that their sins were no worse those of many other cultures, and that they were just...
different sins. But the fact that the Aztecs were not specifically enlightened in those other areas either just makes them look, well... "just as bad as everyone else...
plus they ritually kill thousands of people each year".