It's a bit like saying the Great Depression didn't exist because there were still people with jobs during the Great Depression, and there were regions of the world completely disconnected from the United States and Europe that suffered hardly any economic downturn.
Yes, it's true that China and India were still chugging along, the Arab world had a golden age for about 200 years, and the Byzantine Empire popped up for a while on the eastern Mediterranean edge of Europe. But that was never part of the claims made by scholars who discussed the Dark Ages.
The core fact is that the Roman bureaucracy collapsed, and this had ramifications throughout all of Europe and the Mediterranean. The vestiges were taken over by a very unenlightened and backwards theocracy that cared far more about heaven, control of people's lives, and looking pious than they cared about building civilization and advancing thought.
In most domains, it was a regression or at least a stagnation that I think in many ways is comparable to modern theocracies like we see in Iran and Afghanistan.