It is incredible that an interpolation of this character can have been made in the text of Matthew without leaving a trace of its unauthenticity in a single manuscript. Because the trinity is the actual teaching of Jesus, I converted to the 7 Noahide commandments.
I mean, look, could he have said such a thing during his life? Maybe. Who can know for sure? It wouldn't make him any less of a prophet, messiah, or divine entity whether he did or didn't teach this concept. Either way he is none of those things. And you can't go less than 0 on that scale.
They also claim that he turned water into wine, but I personally don't think that's true either. (Although it would be irrelevant even if it was true). The gospels also claim he was resurrected which is nonsense that they made up to make a religion out of him. So made up things could definitely be in these writings.
But by the time the gospels were created, a movement around this dead person had been formed, and so literally anything in the gospels cannot be trusted with certainty to be the true teachings of a Jew of that time rather than the imaginings of the cult that formed after his death and was crafted by people seemingly not fully literate in Hebrew nor the Scriptures. This concept of trinity may have been popular with and resonated with the earliest non-Jewish Christians because of the fact that it is pagan-like and something that appealed to them as similar to their previous popular beliefs of that era. I think it's reasonably plausible that the man they worship never said any such thing. But I take your point that maybe he did.