Orthodoxy holds itself to be the only legitimate form of Judaism, both now and back through the ages. Jews who were practicing the "right" way were practicing more or less as Orthodox Jews do today. There were some differences in the past, but these were due to circumstance, and were fairly trivial. The differences were sociological and technological, not theological or ritualistic. A traditionally-practicing Jew from any era in the past would recognize the practices of Orthodoxy as his own. As the Chasam Sofer declared in his clever rallying cry against Reform, "Chadash assur min haTorah." Traditional Judaism has not and must not allow change from the correct practices and ideologies, practices and ideas that were given to Moshe on Har Sinia and passed down faithfully by the baalie mesorah. Practices and ideologies that great rabbonim through the ages explained how to observe within the reality in which they lived, but which have been essentially unchanged and uninfluenced by the outside world.
1. Is this an accurate portrayal of Orthodoxy's position?
2. If so, is there some authoritative source, a popular sefer or article or drasha by a recognized figure that I could quote as saying so?