“At what point ate their teachings discounted wholesale?”
When they abandon the authority of God, they are cut off, like cancer by believing churches. Christ did this to churches in the book of revelation.
This also answers your question about when the church deviated from truth. It began before the end of the life of John. It continued. Today, half of what is taught does not find root in Scripture - Apostolic and otherwise.
May I ask why the Pope, bishops, Cardinals, and priests involved in horrific child sexual abuse and it’s coverup are still in power?
Best
Communist usurpation.
Oh, excommunication. So you're plagiarizing that too.(Tee hee.)