So it's your theory that if the Romans were morally squared away and accepted individual responsibility, they would have continued to be able to control Europe and Asia Minor? And how long would that have gone on you suppose?
Let's just take one territory as an example. Germany. The Romans and Germans played a tug of war for centuries. Sometimes the Romans would move into German lands and sometimes they would push the Romans back across the river. How long do you think the Romans could afford to put 1/2 to 1/3 of it's military on the German frontier and contiue to hold the rest of the empire in place?