Doctrine is constantly changing; God's word doesn't. Doctrine is made by man, who is fickle and double-minded; God is neither.
Doctrine can be a good thing, so long as it compliments God's word rather than contradicts. When the doctrine of man is elevated to the status of Scripture, we have a problem. When a church begins defining sin based on its own set of extrabiblical beliefs, it has lost its way. When it preaches Christ is A way to Salvation instead of THE way, it has lost its way. When it elevates the trappings of religion and religiosity over the "religion God finds pure and undefiled" (James 1:27), it has lost its way.
We miss the point because we let doctrine first define, and then separate.
We split the church over dunking or sprinkling, and we miss the point.
We declare Holy Communion exists only inside the walls of the church, or only when we use bread, or unleavened bread, or holy blessed wafers, or red wine, or grape juice, and we miss the point.
We elevate the rich over the poor, and we miss the point. By a mile.
We pull out the parts of Scripture we don't personally like, and we miss the point.
We declare ourselves outside of Israel's law because of Grace, but saddle the Body with laws we invented, because we missed the point.
Doctrine can indeed be useful in defining what we believe, but that doctrine must be informed first and only by Scripture. And doctrine must not be used to separate believers. We must instead look past the surface, into the commonality we have in Christ, and find unity.
If anyone among you thinks he is religious, and does not bridle his tongue but deceives his own heart, this one’s religion is useless. Pure and undefiled religion before God and the Father is this: to visit orphans and widows in their trouble, and to keep oneself unspotted from the world. (James 1:26-27)