I hear what what you are saying. The trinity doctrine was devised hundreds of years after Jesus was crucified. - This fact makes it null and void.
What I'm saying is I can open the Bible today and read that Jesus - was God with us. And I know from experience that the Spirit can't be separated from the person.
So does it mater that someone was able to put the truth together in a package they coined 'the Trinity' 200 years after Jesus ascended to heaven? No, the truth is the truth no mater when you or I become aware of it.