God does not have to cater to your preferences. I'm just noting your reductionist reading of scripture is unique to you and just is based on your philosophical inclination of how scripture should reveal the Son of God as the son of God in essence.
Also, you just had shared that the people in the second century were wanting to hold to Jesus' words of baptizing in the name of the Father, the Son, and the Holy Spirit. So you showed that Matt 28 shared this triune concept right away.
As to your idea of us seeking passages in the scripture teaching the Triune nature of God, we do not look for something saying "the Father, the Son, and the Holy Spirit form the Triune God. We do see Matt 28:19-20 that shows them as distinct but all with one name. But for you to be effective in denying the Triune God would entail addressing verses in scripture which reflect the aspects of the Godhead you wish to reject. Make some convincing arguments to your view.