Well by that standard the 4th or 5th century Roman empire (both east and west) wasn't Roman either. Rome in the 2nd century AD would had probably seemed as alie

Well by that standard the 4th or 5th century Roman empire (both east and west) wasn't Roman either. Rome in the 2nd century AD would had probably seemed as alien to a Roman from 3rd century BC as the Roman empire in the 5/6th centuries was to someone from the time of Trajan. Does that make any of the 3 less Roman? By the time the western empire fell being Christianity and Roman identity were inexorably linked and Latin continued to be the official language until the early 6th century. The Byzantine empire itself changed tremendously as well, while by the time of the crusades it was clearly Greek, before the plague of Justinian and the Arab invasions it would be clearly recognized as Roman (aside from religious changes) by anyone from the 3/4 th centuries.