I am pretty sure you are wrong on multiple counts there.
1. The "dark ages" were called dark because of a lack of written records, after the collapse of the Roman Empire and its centralised systems and imperial bureaucracy.
2. A lot of people did know there had been a different age before. Even if not literate they would regard the literate as the source of knowledge and every village would have some literate people.
3. Life was better for many people. An obvious example was the decline of slavery ( a huge proportion of the population of the Roman Empire) but the descendants of slaves were not the only people who benefitted from the removal of imperial power, and heavy imperial taxes, etc.