I find that view to be reductive and correspond to simplistic stereotypes of the European Middle Ages (e.g., calling them the "Dark Ages"). It assumes people in very different places for 1,000+ years did the same thing and had the same views, then blames the fact that their values are different then ours all on their religious beliefs (which, too, were varied).

This is not to say that tons of material was not lost, or only preserved in other places (e.g., Islamic states in North Africa and the Middle East), but it ignores the learning and innovations of the medieval period (scientific, legal, theological, etc.), and of course the fact that so many classical texts were only preserved because of those monks copying them down.