I would want to disagree that unity is found in uniformity of belief, any more than it’s found in uniformity of clothing, hairstyle, or income.
Is the Trinity vitally important to Christianity? Is the divinity of Christ? It doesn’t seem so, there are Armenians after all. Heaven, Hell, virgin births, resurrections, vitally important? Again, it doesn’t seem so.
A few theologians put it this way and sound much like Pragmatists in philosophy as a result:
There’s not much we can say about what makes a Christian a Christian because the only shared belief among any of them is that Christ atones. The problem though is that none can agree on how atonement works. And so, whatever Christianity means, whatever atonement is, whatever authority scripture may have, we can only see that it all derives from a community’s particular beliefs and embodiment of them, about the Bible, about Christ, about all of it.
Unity is found in love. We may end up like the Pragmatist who says discovering truth is no more than saying we have more reason to believe what we do than to doubt it; not an epistemology, but a mere observation spoken aloud.