I suppose we have all done it. Every believer in Christ is at times tempted to major on the minors. But some Christians seem to have made a cottage industry out of it.
The Christian church around the world agrees on the nature of God and the nature of the Gospel. Groups which get God wrong, or the Gospel wrong, are outside of Christianity.
That's not to say there aren't plenty of other important doctrines of the faith. But some doctrines fall into that "gray area" where biblical Christians disagree with one another on debatable issues.