That ignores that the Roman self-division was one of the fundamental failings of 3rd C Rome, and in the 5th C, Rome lost access to papyrus from Egypt, as well as being sacked by barbarians, and suffering from a century of coerced conversion.This sentence came out a bit hashed up. I'll note that in the Far East, gunpowder came about in the 9th century. The fall of Rome is in the 4th and 5th centuries.
So, there's some significant argument that adoption of Christianity played a significant part in the Fall of Rome. It led to yet another power structure adding to the internal squabbles, and also changed how Rome dealt with its client states. Pre-Christian Rome was expansionist, but not so autocratic. If you paid your taxes and made the required trade goods available, Rome was okay with allowing much local governance. This falls away as the empire starts trying to also force a religion on its client states, and made those states notably more difficult to govern. That's part of why I suggested taking Constantine I out of the picture. The Empire is politically more stable if it isn't trying to force religion on people.
Let us roll this forward somewhat. Rome does not fall in the 5th century. If we also don't have the Christian Church enforcing certain orthodoxy of thought, the end result is... no Dark Ages.
Without keeping the Egyptian papyrus flowing to Roma, (or coming up with paper,) writing, then later reading, becomes an increasingly rare skill, and there you slide into the dark ages.