The fall of the Western Empire wrecked a lot of institutions that were relatively commonplace under one, unified government. Schools, a central army, a sophisticated bureaucracy, and public works such as aqueducts, roads, etc.. all fell into disrepair and collapse mainly because the new "barbarian" rulers were more concerned with survival, seizing wealth, holding onto what they had gained, and in competing with each other than in educating their people or spending their loot in building or maintaining massive new monuments and buildings. It was one of the reasons why it was called the Dark Ages, though Rome's collapse had also opened the way for other new nations to rise up in Europe to eventually attempt to mirror and replace it.
On the other hand, the Roman Catholic Church became a repository of preserved knowledge as a result, though for most everyone else out in the post-apocalyptic decay of the empire's fall, that was little consolation when they were caught between warring factions, raiders, and natural dangers. It's also one of the reasons why the Eastern Empire maintained its power for nearly a thousand years after Rome's fall as it didn't face the same problems, was much closer to wealthier trade routes to bring it wealth and goods, and was controlled by a strong central government inheriting what the Western Empire had lost.
