Well day to day life and your standard HRE setup. Islamic caliphates and Byzantine Empire were set up more like classical civ.
No it doesn't do the same damage cause when you're split in a hundred pieces the scale of civil war's is considerably smaller. And they did have the numbers to dominate the region again the main reason the Middle Ages were so backwards as opposed to earlier is hyper decentralization, the region wasn't united, Germany alone had hundreds of mostly independent entities and that meant governments just didn't have the resources to do what they did in the classical civilization. And the church maintained a lot of the staples of classical civilization but the church was also(literally) walled off from the rest of society.
Well classical civs(Rome, Persia etc basically civilizations pre dominance of Islam and Christianity) weren't industrial but classical civs were kind of like modern life if you take away industrial technology, socially things were pretty similar to today while in Europe.....not so much. It's very hard to put a clear answer to your question in words though I have a clear picture of what I mean. But the building of churches took an incredibly long time and the number of churches that were architectural marvels were relatively few in number. Worship was also society's number one priority and like I said before the church was sort of an isolated time capsule into classical life in many ways. They did not advance further than classical civs and if by the end of the Middle Ages there were areas where they had(I guess guns would be an exception, they came at the very end though) it sure as hell wasn't fast.
