What's so idyllic about living a lifestyle that is barely at a subsistence level? Being under the constant threat of starvation should the buffalo fail to show up in the tribe's hunting grounds doesn't seem to be a very idyllic way to live.
In her book The Discovery of Freedom: Man's Struggle Against Authority (New York: Day, 1943), Rose Wilder Lane blamed the extreme poverty of the American Indians on the "communist" lifestyle practiced by most of their tribes.
To be fair, the Aztecs had a very sophisticated society by Stone Age standards.
Aside from, y'know, the whole human sacrifice thing.