Modern Theodosian civilization does not rely on magic, it relies on science and technology. Bianka invented the Steam Engine, Qunari invented gunpowder as well as Gaatlok cannons, Branka invented smokeless fuel, etc. Heck, Bianca the crossbow is a lot like gun.
Additionally, in real life, we are where we are now because of science, not because of associative magical thinking.
Source:- http://dragonage.wik...ki/Bianca_Davri
... Do we really have to go through this again?
In short: science is a tool to study nature and technology is a byproduct of us using it appropriately and expanding our knowledge on the universe. In Thedas magic is a part of the universe. So naturally in Thedas magic IS a part of science and technology! Heck, dwarves were even the one who invented enchanting - stuff that most definitely requires magic in form of lyrium.
In fact all things point to Arlathan being a highly technologically advanced, scientific-minded civilization. Not only Solas displays scientific mindset - in Vir Dirthara we find numerous codices focused on research of magic and world, while in Corssroads we find Ghilan'nans scientific experiments involving advanced enchanting.
In other words, you couldn't be more wrong. The irony of Thedas is, in relation to our world, that "ancient world" resembles our civilization more than current state of Thedas. When you read about Arlathan and listen to Solas it's becoming obvious that ancient Arlathan is a cautionary tale for us about exploits of advancements of technology and power that it brings.
Okay, the ancients know a lot. So what ? What's stopping us from starting the Industrial Revolution in Thedas now that we have the Steam Engine ? That's right, Ancient Mages mucking things up. Why do we need to rely on magical relics from a failed civilization brought down by the hubris of their leaders when we can make our own living just fine without them ?
Like I said, people muck things up, no matter of world state of situation. Did you know that we had first experiments with rudimentary steam engines during times of frikking ancient Greece? Guess what mucked progress for almost two millenia, before age of Enlightement? Us and our adherence to silly religious dogmas and stifling of innovative thought.
What's more the progress in Veiled world has more definitely been stifled, sometimes for centuries. It's hard to be innovative in the shadow of Archdemon's wings or when Darkspawn are gnawing on your newest project, together with your fingers and head and occasional family member.
Plus - you realize that necessity is a mother of invention? I mean, what would ancient mages need steam engine for? What would they need stuff like eventual cars or airplanes for if they have eluvians and magic able to lift terrible weights to transport them safely and quickly to the very edges of the continent in a matter of seconds? What would they need syringes or blood transfusion when healing magic can bring someone from the brink, or sometimes beyond? What would they need computers or Internet for, when they have pretty much a natural version of it, far superior to what we currently have?
In other words - why would Thedas need to go through Industrial Revolution the like of we have? What if part of that Revolution means realizing at one point that magic is essential for civilization to progress, given that magic IS part of that world?
And what stops them from mucking things up later, when they go past steam engine and reach Thedosian equivalent of nuclear weapon? What about the fact that even in our world the clash between old and new civilization brought about two devastating world wars and we never know if we wont' bring down the third on our head, as well as eventual end of our civilization, since you only need a fraction of our available nuclear arsenal to wipe us from this planet by initiating devastating nuclear winter? And if all of it goes kaboom at the same time, we're talking wiping the life to bacteria level for at least a couple of millenia.
This is exactly why I say that we should look at Arlathan as OUR world gone wrong. This is also exactly why I say that the whole "mages mucked things up so we should get rid of them and likely magic as well" as super-naive, because eventually - in a scenario where the world actually goes about without any other cataclysm waiting for it - the civilization will catch up to a point where it can destroy itself easily. I mean... what are people going to do then? Shrug helplessly and be all like "oh well, we had a chance to learn how to wield great power responsibly, but guess what - we mucked this up!"?