The key point at which the doctrine of the Trinity and all the doctrines that compete with it (including ones which see Christ as divine, such as Oneness or Modalism) get off base is in choosing God the Father as their starting point. This is anti-biblical.
The Bible directs us to make Christ the starting point (and ending point) of our understanding of God. He is the Alpha and the Omega, the Beginning and the End. God established that Christ should be the centerpoint of all our thinking about God.
No one has seen God at any time; the only begotten God who is in the bosom of the Father, He has explained Him.
(John 1:18 NASB, underlining added)
If you start with the Father, you can’t always get to the Son (look to Rabbinic Judaism if you doubt this). However, if you start with the Son, you always get to the Father.
On the Mount of Transfiguration, the voice from the cloud said of the Son, “Listen to Him!”
When in Deuteronomy 18 Moses spoke of the prophet God would raise up after him he said, “To Him you shall give heed in everything he says to you.” (italics added)
When Peter quoted Moses on this point in Acts 3, he also made clear that Jesus was the One to whom all eyes should now point.
I could go on and on. If God took such pains to point us to Christ, why do we look elsewhere for the foundation of our thinking about God?
Thus, the alternative to the doctrine of Trinity (and all the systems that Trinity adherents label as error) is not unity per se, but rather Christ Himself. “In Him are hidden all the treasures of wisdom and knowledge” – we should not be surprised if we do not find all the treasures of wisdom and knowledge when we look in other places.
To learn more about Christ versus the Trinity, see: