The Israelite's had God's Laws delivered to them, seeing the fire and the smoke, watching the death angel kill, seeing rivers of blood, and a sea split, and yet most of them refused to walk in the instructions of God.
The Jews had in their possession the Oracles of God for centuries, and yet when Jesus came to them, they were preaching for doctrines the Commandments of men. Constantine founded the religious doctrines and traditions of the first Catholic religion which flourished for centuries, unchallenged, until the reformation, when the scriptures they had the whole time, showed them they had been wrong.
There is no question that "Christianity" has been "wrong" for centuries, just as the mainstream religions of this world have been wrong since the tower of Babel.
Just because you might adopt an ancient religion which calls Jesus Lord, Lord for Centuries, doesn't mean you are on the Path Jesus said to Walk. Any more than Jews who followed the mainstream God of Abraham preachers of His Time.
A man will always side with the choices he makes, and will go to great lengths to justify them.
Abraham followed the religions of his father for 75 years, but when HE heard the Word of God, he became a "Doer of the Command" and followed God.
It doesn't matter about religions of this world, regardless of how old they are. We are still to be "doers" of God's instruction, not just hearers, regardless of the religious philosophies of this world.
Luke 8:
21 And he answered and said unto them, My mother and my brethren are these which hear the word of God, and do it.