Valid points. I had origionally considered that Technomancers used magic to produce their wonders.

But then I remembered a quote from a time-travel story:

You can't railroad until it's time for railroading.

The idea is that technology can't progress beyond the infrastructure that supports it. This means that farmers have to produce enough surplus to support millions of workers who do not farm. These non-farmers have to mine, refine, and manufacture the feedstocks of the mass industrial efforts which produce the technological miracles. Other non-farmers have to move the food, fuel, and fun around from where it's created to where it's wanted. Add in managers, entertainers, teachers, police, and soldiers, and you discover you need tens of millions of citizens to railroad, and hundreds of millions for cell phones.

Without the supply chains, knowing everything you need to know about computers does not get you on-line. The other guy needs a computer too. And a wi-fi router.

So, I went with individual tinkers playing with relics under the eye of a jealous Technomancy Guild. Their technical miracles are one-off creations using half-understood theories. They can't create a second lithium battery because all of the available materials went into making the first.

And the Guild watches its members and the dabblers too out of fear that they might waken the sleeping giant which had previously destroyed their world.

Of course, the original post I made was intended to provoke thought. The worldbuilder is free to use what he likes and discard, modify, or recreate the rest.