I think it because of the distribution, it doesn't spread evenly, unlike in Fontaine, where technology is commonly used and distributed evenly, Natlan is kind of different. The characters uses sophisticated technology more than characters from other nation including Fontaine yet it's not apparent in the nation itself.
In Natlan it seems that there are great disparities between the things that is advanced and that isn't, there are no public transportation in Natlan unlike Fontaine, yet Kachina has drill-like vehicles, Mavuika has a bike, and Chasca has a flying rocket like gun.
In Natlan, they make such simple, traditional buildings like those in rural areas and some of their weapons are traditional, like the melee ones, yet they have saw-machines, guns, and vehicles owned by some characters as if they were an industrial nation.
Now if you saw a place where the aesthetic of their buildings are mostly traditional and made out of simple materials, you would be surprised to see there are people dancing to DJ, riding a bike, flying rocket gun, having giant guns as weapon, and drills.