How much truth is there in this version of events? Not a great deal I would say. In the specific local case of Mesoamerica the initial cataclysm was more akin to a confrontation between two ruthless imperial powers, in which tactics and microbes ultimately made all the difference.
We tend to forget that Mesoamerican society at that time was remarkably similar to that of late medieval Europe in terms of its social stratification and inequitable sophistication.
Seville, then the largest city in Spain was but a quarter of the size of Mexico-Tenochtitlán. The rich of this city had a fairly diverse diet while the poor had to make do with around three pounds of maize a day, ground into tortillas. While there was near-universal education, the high-born had exclusive access to special schools called calmécac. If this is a "lost way of being human", it is nevertheless a familiar one.
Only members of the nobility - the pipiltín - could drink chocolate or wear cotton. Sumptuary laws further specified that the upper classes alone could use glazed pottery or could sport cloaks that hung below the knee and that the poor had to shed their sandals when in the presence of their social superiors.
The bulk of the population of old Mexico were labourers characterised as macehual, most of whom had right of access to a specific plot of land which they could pass on to their children. They tended to be organised into calpulli, a cross between a clan and a guild, but in the last century before the arrival of the Spaniards the growing wealth and entrenched power of the elite had started to diminish the influence of these collectives.
The second largest group, roughly a third of the population - were mayeques, a class equivalent to the European serfs who spent their days working on land that belonged to someone else. Poets described them as 'bumblebees' that buzzed around at the edge of public celebrations waiting for the customary handouts of maize stew*.
It is believed that many of the mayeques were descendents of people that had been living in the valley of Mexico before the comparatively brutish Aztecas of Aztlán showed up. Those not thus subsumed into Mexican society were often forced to devote their best fields for growing produce for the metropolis in a manner that forshadowed the Chinese land grab in contemporary Africa.
Drunkenness among urban labourers was reportedly on the increase in spite of a strict law that decreed death for two-time offenders. Only grandparents over 70 were exempt. The young and the poor were theoretically prohibited pulque except at certain festivals. Adultery was also a capital offence.
The Mexica's use of a 360-day calendar - the Xiuhupohualli - meant there was a section of the population born on one of the five apparently useless days in the solar year who were basically considered doomed from birth. (And if you were born on the day of 2-Rabbit you were probably even more screwed.)
By far the worst aspect of being at the bottom of the social ladder in old Mexico was that in the early sixteenth century this was increasingly likely to mean death on the sacrificial block. During the period of military expansion a hundred years earlier under bellicose deputy-emperor Tlacaelel, it was more usually battle captives who were picked to perish under the obsidian knife (actually flint, because obsidian is brittle and thus better as a metaphor). Then, as imperial rule settled into a more stable pattern, tributes - often children - were sent by the subjugated to be sacrificed. But Huitzilopochtli grew ever greedier for blood, and so the numbers had to be made up by ripping out the hearts of Tenochtitlán's own plebs - all of them sold the dubious 'espejito' of thus departing for Omeyocan, the VIP paradise reserved for those who died the 'flowery death' and not Mictlan, the grey airport lounge of annihilation occupied by more conventional cadavers.
The Nahuatl word for sacrifice, nextlaoaliztli, means act of payment, and in old Mexico, as in old Castile, a key aspect of being outside the elite was not being fiscally-exempt, yet here there was the additional anxiety that one's own person could form part of the tribute system.
So, one has to ask, were the dirt poor indigenas of these parts really having it so good before the bearded men from the east arrived?
* Remind anyone of posadas today?