Your #1 was closest to what I was thinking, which was simply that trying to compare a sedentary culture in a modern nation state to an ancient culture in the time long before major migrations ended is just ridiculous. But even deeper, the idea that those migrations were somehow responsible for the fall of Rome...I mean, the barbarians saved Rome. They gave us the Holy Roman Empire. France, Spain, England. It's tempting for classicists to look back and imagine the best of the West copied Athens and Rome and preserved some ancient genius, but they didn't. The West was founded by the barbarians.