It absolutely is the teaching of scripture and it defines Christianity.
While you are correct, "the church" has, in its variety of organizations, come up with some rather odd notions of what is essential Christianity, some of which border on absurdity.
But, the reader of scripture who, for some reason, concludes he is mor capable of understandint what Jesus and Paul et.al. meant based on his understanding of his English translation, than were the people who generated the Creed and that he understands the scriptures better than they did is demonstrating an extreme level of ignorance and arrogance. They spoke the language in which the scriptures was written and did not have to depend on a translation into a modern, western language from an entirely different culture. They lived in the culture in which the Church was established so they understood the nuances of the Greek which cannot even be translated into English.
The result of that ignorance and arrogance can be observed in the existence of tens of thousands of denominations all claiming to be right in spite of Jesus explicitly stated will that we be one (Jn 17) and Paul's admonition to the Corinthian church (
1Co 1:10) that there be no divisions among them.
It is an act of rebelliousness (which is like the sin of witchcraft
1Sa 15:23) for any individual to assume and then declare that they know better than the people who hammered out the doctrines of the Trinity in the early years of the church in the face of multiple heresies in the face of threat of exile and death.
It is a testimony to the ignorance of those rebellious people that they consistently come up with the same heresies that the early church went to such great lengths to refute and it is evidence of arrogance for these rebels to boldly state that it is the Holy Spirit who has revealed it to them as the true meaning of scripture.
It is these rebellious people who have "blessed" us with the Mormons, the Jehovah's Witnesses, the Christian Scientists, the "oneness" churches and every other popular heresy used to lead people to hell today.
There is truly nothing new under the sun. That same mindset that assaulted the Church with Arianism, Nestorianism, Docetism, Apollenarianism, Modalism, and every other early heresy that is simply reintroduced by the devil through the agency ignorant and arrogant people who believe they "know better" than those who put their lives on the line for the truth many centuries ago.
I find it shocking when someone without any formal theological training declares that they know what scripture teaches better than Athanasius and Basil and Gregory of Nyssa and Gregory Nazianzus and Cyril of Alexandria and John Chrysostom and multiple others who fought, some to the death, in order to preserve the teaching of the apostles which they were taught by God with us, Jesus.
Christianity comes to us a a whole piece. We do not get to remake it according to our personal interpretations.
The creed is what is exactly what is meant in the ToS by the words: "historic Christianity." It is the universal teaching of the Church from the beginning.
OK - end of rant
iakov the fool