Doctrine matters, and no doctrine matters more than the doctrines concerning Jesus Christ.
One of the earliest and most intense controversies in the early church had to do with Arianism. Arius taught that the Son of God was not equal to the Father, not eternal God, but only a very exalted and powerful creature. He was not always with the Father, but there was when he was not.
So what? What does it matter whether Jesus was the eternal consubstantial Son of God or not?
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