Woah, woah, OK, calm down. Grell74 has a point, actually, it's just a DIFFERENT point from the one most people are thinking about.
When Johan said that this DLC didn't take resources from anything else, he was GENERALLY referring to stuff like republics, theocracies, pagans, etc. - in other words, meaty gameplay changes that take designers and programmers to crack. This was in direct response to people complaining that "You threw over playable republics/theocracies/pagans/comets for THIS?!" "No resources were wasted" because the artists and scripters needed to work on this Aztec mod wouldn't have been able to help with that kind of thing to BEGIN with.
What Grell is suggesting, however, is that instead of modeling and scripting for Aztecs, these artists and scripters COULD have been drawing orcs/elves and scripting appropriate events for such. He further suggests that this would have been a lot handier to the community because there's a number of fantasy mods out there now that COULD use fantasy models and shields and are unable to insert these themselves, since existing Paradox modding tools don't support that. Heck, he even suggests that instead of fantasy, they could well have drawn things like Indian or Japanese units that modders could make use of. As such, the artists and scripters were "misspent" working on Aztecs when they could have been making elves/orcs/dwarves/Indians/Japanese/fanboy models.
This is entirely true, and he is entirely within his rights to be disappointed by the specific choice of things Paradox decided to model (and sell). That said, I can't help but think that the more historically-minded fans would have been just as furious and outspoken if the DLC HAD been about a fantasy invasion of some kind - it's true they say that fantasy would have been better now, but that's with the benefit of comparison. If they hadn't known that the alternative was Aztec invasion, would those screaming for republics really have been happier with the outbreak of the Dwarf/Troll wars in Scandinavia and the premature rise of Count Dracula? As for modeling units from other parts of the world, well, I don't personally know what the comparative popularity of nations is in the modding community, but hey - at least the guys hoping for a Mesoamerican mod are going to be happy, right?
I think it's pretty silly to assert that Paradox artists should spend their time making art specifically for modders.