Also, life expectancy collapsed, Diocletian instituted what became near-universal serfdom, population density feel by a third (maybe nice if you were born afterwards, but can't have been super fun for the people watching their progeny diminish decade by decade), and the loss of learning inside the Empire was so complete that medieval Europeans called their standard text on astronomy the “Almagest”, its Arabic name, even though its author Ptolemy lived in the Roman Empire and presumably wrote in Greek; only Arabic translations survived. (Some other books only survived in Ireland, outside the former Empire.) The Romans were no scholars—think of the detestable Sulla or monstrous Marcellus—but what came after was far worse.
From the point of view of human rights, of economic prosperity, and of scholarship, the collapse of the Western Empire began a disaster that lasted nine centuries.