So, getting through some of this: Ixis has a very big point of this. Intelligence, the ability to solve complex problems, has not really changed. Between then and now, we have plenty of advances that doesn't make us smarter, as much as it makes knowledge more widespread. It isn't the few scholars who can read and write anymore. Anyone who wishes to learn can usually find a way, and those who know are usually willing to teach. We also have more knowledge today than we did back then. Losing technology would not take that away from us. Not all of us know how to hunt, but those that do could would hunt, and would teach. We'd already know how to write. If you took our books and our paper, we could still find other ways. Plenty of us learned how paper is made in elementary school. I'm sure we could dredge up those old memories. And once we had paper, why did we need to go back to scrolls? Plenty of us can sew, and there are plenty of things to make thread and paper from. Heck, you can do it with celery.
And even without all of that, we'd still have knowledge that the ancient peoples didn't have. Without books, without technology, many of us would tell it to our children. Even if we didn't rebuild for hundreds of years, those who cared would teach the neonates to read, and write, and would talk about genetics, atomics (I'm thinking about atoms and molecules and such, but I don't know the true name for that study other than science), psychology, biology, astronomy, history and government... It's possible that knowledge would once again become the property of a select few, but it would still continue on. Plus, they would still have the knowledge of the history of the ancient Greeks and Romans. Their culture, their religion... And some would welcome the challenge of figuring out how their inventions worked, using schematics they'd burned into their brain out of fascination, and those would be easily built.
Really, I'd say that in the end, that gives us a leg up on the Greeks and Romans.