They were not in error. The Eastern Orthodox Church continues today and is doing quite well. When Lutherans came to the Orthodox patriarchs trying to convert them to Protestantism they shamed them for becoming sectants and turned them away.
The 7 seven in ASIA were CATHOLIC; not EO.
They WERE in ERROR for the BIBLE says so!
You have a MASSIVE case of BaghdadBobism.
Hie thee to a nunnery!