I read the original post to be asking and exploring whether the Trinity doctrine has been a net asset or liability to Christianity, its purpose, mission and spread.
And that's a profound question. I eventually came to the conclusion that the Trinity doctrine gives its believers an advantage in appreciating the Lordship of Christ, while rejecting the doctrine gave us an advantage in appreciating his faithfulness, obedience, commitment and sacrifice. I'm not impressed by a sinless God. I am impressed by a sinless man.
I can say I certainly found it easier to believe Jesus was a man than that he was God. Too much didn't make sense, and I have to wonder how many people over the centuries have rejected Christ in their hearts because its central claim, that God became a man, was so absurd.
But you could say that about a lot of beliefs. The virgin birth, for example (or virgin conception). The Great Flood. Lots of beliefs. Is the Trinity really that different?
Of course, Johniam's question is also a spiritual one. He sees the trinity as spiritually harmful to those who believe it. So to agree with him is to reject the trinity, and you must disagree with him if you embrace the Trinity.
Is it an asset or liability? Does believing it make you a better Christian or does it hinder your walk? Well, that depends, doesn't it?
I believe the earliest Christians were not Trinitarian. Paul gives us a Jesus who is subservient to the Father. In fact, Paul speaks nothing at all about Jesus' earthly ministry [the last supper being the only real exception]. Paul is much more concerned about the spiritual aspect of Christ's ministry, the "principalities and powers" behind what took place on Earth. Jesus wasn't crucified by the Jews, the Romans, or Pilate. He was executed by "the princes of this world," which is not a reference to human beings.
What's interesting, then, is that the Christ of this spiritual storyline is referred to as "the firstborn of all creation," which can be interpreted a number of ways. The way most consistent with TWI Christology is that Jesus was first... not chronologically, but in order of importance.
But other Christians take it literally. Jesus being the firstborn of all creation, to the Jehovah's Witnesses, means that he was the first being created by God, and the agent by which God created everything else. Yahweh and Son, from the beginning.
To Trinitarians, that is not a creation of Jesus but a begetting, and it's something that happened before there was any such thing as time. It's not something that can be explained. Just accepted. So there.
So what's all this mean?
I believe it demonstrates that the New Testament tells two separate Jesus Christ stories. One is down to earth, and the other is, for lack of a better word, cosmic.
It becomes easy to see why the early church couldn't settle on his identity. The two stories are not compatible except when one is recognized as metaphorical from a human perspective. Unless he really is God or the first creation of God.
Obviously I'm in no position to answer whether the doctrine has helped or hindered God's plan. I think BOTH stories are made up, one largely and the other entirely. But I am fascinated by the exploration of the question.
Enjoy.
While you can.