There's obviously the running trope of the vastly superior race nuking anyone getting too technologically advanced - in this case, Khaenri'ah - but I was always struck by the sheer technological difference between Khaenri'ah and the rest of Teyvat.

The one extant nation shown so far to have advanced technology is Snezhnaya, and that's mostly because they're reverse-engineering Khaenri'ah's tech and have some of their refugees.

For the rest? Technological advances have been basically nil. Khaenri'ah could build machines that still function perfectly after 500 years and zero maintenance, obviously had deep understanding of very complex subjects such as literal rocket science, and were overall so advanced that even compared to real life technology they still pull ahead in most aspects.

Meanwhile, even after 500 years of possible advancements, the rest of the world still has fucking Middle-Ages tech.

It's already been discussed here how Visions could actually be a wail to corral overly-ambitious people, and I think this is a major contributor to the lack of progress - everything uses the Elements.

Need heat? Pyro. Need healing? Hydro. Need energy? Electro. Moving structures? Geo, and so on.

Anytime a problem arises that would require technological advancement to solve, there's conveniently a Celestia-approved element that can solve it, and a Celestia-appointed Vision holder to do it. Humanity is never incentivised to not use Elements for literally anything.

Since technological advancements builds off of previous technological advancements, having every problem get a tailor-made, punctual Elemental solution means that those building blocks effectively don't exist.

Kinda like how races in Mass Effect were tricked to base their entire tech around the Citadel, and not develop new kinds of tech the Reapers couldn't easily counter, everything people of Teyvat use is based on the seven elements.

The only outliers being, obviously, Khaenri'ah; none of their tech is overtly based on the Elements. That factory from Childe's story quest doesn't use any kind of Geo or Electro mechanisms, just pure machinery. Ruin machines don't use Elements to power themselves or to attack.

Not using company-approved wares also mean that they aren't subject to the hidden limitations of said wares - Celestia had no hold on their advancement, couldn't throw technological dead-ends at them to prevent discoveries.

This would also explain why the Tsarista is so interested in their tech - I would assume that it's literally impossible to overthrow Celestia with conventional use of Celestian tech (Visions and Gnoses), so she's cooking something up that could work outside of the almost certainly present hidden failsafes of the Elements.