I would agree with that stance and that classical antiquity ended then. But you still have to acknowledge that the Roman state, its culture and institutions not only survived but arguably came out even more dominant (with the exception of pagan religion), e.g. with a second political stronghold in the East.

There are many episodes in Roman history that people would have experienced as decline or even collapse within their lifetimes, including multiple sackings of the city of Rome itself. But in most of those cases things actually did bounce back and the Empire continued to dominate. That's kind of the point I was making. Empires would seem to be far more resilient than contemporary observers would think if one only looked at Roman history. But the problem is that the Roman Empire is a bit of an outlier in that regard. Ancient cultures of Central America would be interesting to study there (there were far more than just the Mayas, Inkas and Aztecs, most of them relatively short-lived, hence good case studies for the question of collapse). Unfortunately much less is known about them than about Romans.