Patrick Navas sees John 3:16 teaching the subordination of Christ to God. That's to say Christ was sent to the world by God. He doesn't find it teaching Jesus to be consubstantial with God.
Patrick Navas felt texts Trinitarians appeal to were simple to counter.
His three main points against the Trinity belief:
1. Doctrine of the Trinity is not articulated in the Bible. Trinitarian theologians admit this.
There's a distinction between Biblical Christians and Creedal Christians. Those claiming Sola Scriptura and keeping the creeds aren't really being true to the idea of Sola Scriptura.
2. Identity of God and Jesus distinct from each other.
In 1 Cor 8:6 Paul spells out the identity of God and identifies Him as the Father:
yet for us there is but one God, the Father, from whom all things came and for whom we live; and there is but one Lord, Jesus Christ, through whom all things came and through whom we live.
In Acts 2:36 Peter is purported to have said:
"Therefore let all Israel be assured of this: God has made this Jesus, whom you crucified, both Lord and Messiah."
The authority Jesus had was not due to his ontology but rather it was given to him by God. A derived lordhsip. The "lord" has a God. Jesus has a God.
3. Holy Spirit
There are some texts (mostly in John) which ascribe personal qualities to the Spirit but those texts can be understood as personification as per Wisdom in Proverbs 8.
[Note: The Jews, as articulated by rabbi Tovia Singer, believe the Holy Spirit is the active force of God]
Through Gregory of Nazianzen, as late as 380, we see there was a running debate as to what to believe about the Holy Spirit. How can there have been a Trinity teaching passed down through apostles concerning the Holy Spirt if Christians were undecided on what to believe about the Holy Spirit?
"Gregory of Nazianzum could still say in 380, Some of our theologians consider the Holy Spirit to be a certain mode of the Divine energy, others a creature of God, others God Himself. Others say they do not know which opinion they ought to accept, out of reverence for the Scriptures which have not clearly explained this point."
If the Trinity is not explicitly taught in the NT how can it be reconciled as an essential teaching of Chrisianity?
Tovia Singer: Does the New Testament Teach Jesus is God?