The creeds you had cited were all the result of a group of theologians getting together and arriving at a consensus concerning a theological issue. The earliest Christians were not governed by these creeds, but they were clearly followers of Jesus Christ.
You raise some excellent points.
Frankly, I am surprised that no one here has commented on the three passages in the Bible where the word Christian actually appears. The first is found in Acts 11:26: "And the disciples were called Christians first in Antioch."
So Christian was first used a synonym for disciple: "a follower of Jesus Christ."
Can you imagine if even our President, who is a Christian, decided for political reasons (just as Constantine did) to gather all the disagreeing leaders of various Christian churches, faiths and sects and crafted one single religion with an overarching creed out of what came out of that meeting? Would YOU want anything to do with that religion? And if you believe your current religion to be true, then what of this new religion? It changed some major tenants of your old religion, and compromised many others, so the new one can't be true, right? This is precisely what happened in the 4th Century, except that the guy behind it all was a Roman Emperor who may or may not have even been Christian at the time.
If the church established by Christ was even more altered and even warped then, and its true form and doctrine was lost, don't you think it necessary that it later be restored? It was. And it happened on April 6th, 1830 after God the Father and His son Jesus Christ visited and directed that it be restored after the long apostasy.