Yes im talking about this again, cuz I'm interested in world-building. Now, there are 2 things that I THINK make sense for Natlan to be technologically advanced.
It is a nation of War
It's relation to Energy (because fire or fire-related thing)
Now, I want to compare this to other fiction, this is just a comparison, not off topic.
Let's look at the Fire Nation from Avatar The Last Airbender.
Lot of people have expressed their opinions on why Fire Nation is the most advanced but I'm going to bring my opinions here.
1. War
The needs for war would pressure nations to make advanced technology and I think this happen in real life. In the case of Fire Nation, they want to invade and achieve world domination, ofc they need some kind of technological and industrial power to achieve that. Machinery and advanced weaponries will be required to increase military strength.
2. Fire
In technology, metal is an important component, but to manufacture it it requires methods like smelting. How do they achieve this? Obviously they use firebending.
Then they make vehicles and machines, but how do they power them?
Since in ATLA Fire Nation uses steam engines, they need fuels such as coals, and to generate energy you need to burn them, Fire Nation just have the thing.
So Fire is important because it's a direct versatile energy source, it can be used for heat and propulsion like in powering engines, machineries, and for manufactures.
The combination of their knowledge of energy uses, the vast availability of energy and the pressure to advance for war, make Fire Nation the most advanced nation in ATLA (back then metal-bending haven't exist yet).
Now let's look at Natlan
Are they in War?
Yes
Do they have a reliable energy source?
Yes, Phlogiston, and this is supposed to be more advanced and even more versatile because this is a fantasy based energy unlike Fire Nation where their uses of energy is based on real life (using fire to power steam engine).
But the problem is that it does not fit to Natlan tribal aesthetic, and the inconsistencies because their technologies are exclusive to vision holders, they don't use this technology in other things, so it just looks weird because of the disparities.