Market forces and social and business demands drove the creation of such devices, and not, as Postman might have argued, the other way around.

I can't find the argument you appear to be responding to in the essay you linked to. However, technological determinism shouldn't be wholly dismissed. It may describe only one aspect of technology, but you can't argue that technology doesn't alter society, nor can you argue that the maintenance and support of that technology doesn't require many, if not most, of us to spend an astonishing amount of time, energy, and resources ensuring that everything our technologies require is provided to them. So it would certainly seem that technology is at least one significant factor which drives our social structures and cultural values.

Postman is suggesting he looks back, with great nostalgia and envy, at a time when we were forced to ignorantly accept whatever we were told, with absolutely no recourse for informing ourselves.

I'm afraid that my reading of the essay was much more like Wikipedia's description of it:

He also compares contemporary society to the Middle Ages, where instead of individuals believing in anything told to them by religious leaders, now individuals believe everything told to them by science, making people more naive than in Middle Ages. Individuals in a contemporary society, one that is mediated by technology, could possibly believe in anything and everything, whereas in the Middle Ages the populace believed in the benevolent design they were all part of and there was order to their beliefs.

In any event, the article originally posted was bemoaning the extent to which Americans pay attention to their phones instead of their environment and each other. I've noticed the same phenomenon and worry about where our technology might be leading us.