Why do some Christians use the New Testament but deny the early church ecumenical council doctrines?

Most Christians do not doubt the authenticity and inspiration of the New Testament. Most Christians agree that the New Testament should be treated as inerrant and authoritative. Most Christians know as a historical fact that the ancient united Church carefully determined which New Testament books were canonical. And most Christian also know that this same Church also confessed God as Holy Trinity, among many other canonized teachings and doctrines. But, if one does not want to interpret the Bible through the hermeneutic of Nicaea-Constantinople... or through the hermeneutic of the other canonized doctrines and teachings... how can you accept the New Testament at all? After all, neither the Old nor New Testaments fell from the sky. --- P.S. I am **not** referring to any councils after 1054 AD (Great Schism). So let's all understand that this is not about "the Western/Catholic/Roman church" nor "the Eastern/Orthodox/Byzantine Church" which then started to exist independently of each other.