I would not call Trinitarianism a heresy, more a misunderstanding, like doctrines which Trinitarians have called heresies. Some might have been due to pagan influences such as Neoplatonist hypostasis, which the philosopher Origen applied to divinity (apparently ignoring the command of God not to do so). Trinitarian dogma ended up confounding or occluding the teachings of Jesus Himself about how divinity applied to Him. So today we have Trinitarians telling us confidently that Jesus is God, obscuring the whole truth of Jesus being a man born of holy conception from God by the Holy Spirit and becoming set apart by God to judge Mankind and mediate between Mankind and God. It also hides the true nature of the spirit of Christ being a great influencer of prophets from earliest times, even long before coming in the flesh. Perhaps the sticking point started with Trinitarians trying to use human concepts to understand how Christ shares some kind of special relationship with the Father, God, by the Trinitarian founders trying to apply a Greek concept of shared substance of nature existing between Jesus and God the Father, as if divinity could be reduced down to natural substances like gold or silver elements. Of course, God commands we do not think of Him in that pagan way. We must not use the kind of thinking and philosophy which pagans apply to their idols. This pagan thinking seems to have resulted in Trinitarians bringing to the table their idea that somehow the Son and the Father are composed of some special kind of material. This kind of Trinitarian dogma harms our understanding that Jesus was born with a human body exactly the same as our own human bodies, and has soul and spirit like us. Yes, the spirit of Jesus is immense in influence and power, growing to fill all things, but Jesus is like us, nonetheless, meaning we too can grow immense in influence of our spirits over matter and time and space, once God sets our spirits alive through the sacrifice of Jesus and our faith in Jesus and in God. We can do greater works than Jesus if we believe, now Jesus is with the Father, Jesus said. Some of us see that being fulfilled in our lives now and know this is but a foretaste of what is to come, especially after Jesus has returned. Truth matters. Untrue thinking clouds truth. It clouds understanding of truth. It needs cleaning away. Truth sets us free from the slavery we get from our vices. We need to turn from false thinking and embrace what Jesus taught and those sent by Jesus taught. We need to believe in this and believe in the true Jesus Christ the Lord.
