I believe a lot of historians get rather upset about the use of the term 'dark ages'.
The Romans used their professional army to destroy many of the cultures unfortunate enough to be within their reach (Dacia, Carthage etc). They then wrote the history to make themselves look good and the 'barbarians' look bad. Consequently the fall of the Roman empire is seen as a disaster. But the Romans were a brutal bunch. They used to watch people being mauled by wild animals and gladiators hacking each other to death as entertainment, after all. Many of the people that the Romans conquered must have been glad to see the back of them.
If you look at the history of Western Europe after the collapse of the Roman Empire you'll find that Society largely collapsed into small towns each governed by their own local Lord or perhaps a king but constantly subject to attack from all sides by neighboring powers in distant foreign powers who would occasionally sweep through and murder every one except for the desirable women and children. Occasionally a man's life might be spared if agreed to be a slave or serf for another Lord or King. The situation was exacerbated by the effects of the Justinian plague and the onset of volcanic winter in the year 536.
This is a very modern reading of a very ancient situation.
By the time of Western Roman Empire collapsing, the realm was Christian for two centuries and gladiator games et al. were banned for so long that no one alive would remember them happening. Most of the local languages were also gone and the previously conquered people considered themselves Romans and spoke Latin. They didn't have any Wikipedia or nationalist schooling system to teach them that they were once Celts or Illyrs, 400 years ago.
(Even in our modern world where history is taught and movies and books are abundant, few people have any idea of who conquered whom in 1620 AD and what were the consequences for their distant ancestors. This is a domain of history geeks. No modern German loses their sleep over whether his city was once plundered by the Palatinate forces or burnt to the ground by a Saxon army, and would not dismantle modern Germany just because such atrocities once took place.)
Also, the Roman empire did not dissolve into a vacuum, with the previous provinces simply declaring their long desired independence. It was conquered from the outside, and the attackers would not necessarily treat the subdued population any better. They might, or they might not.