Indeed, the Eastern Orthodox, Oriental Orthodox, Lutheran, Anglican, Methodist, Roman Catholic and Assyrian churches have never at any time even collectively comprised a majority of the human population, but they have collectively comprised the largest religion (historically, the largest church was the Assyrian Church of the East, which spread from modern day Iraq north through Persia, and then East across the Silk Road to Mongolia, South through China and to Tibet, and also into India, and then south from Iraq to Yemen and the Island of Socotra. Before Tamerlane began systematically exterminating Christians in a genocide continued by his sons, the Assyrian Church was vastly larger than the Roman Catholic Church in geographical area and also likely larger in terms of total membership. Before Islam, its only rivals were the Manichean religion, which was a heretical Gnostic religion designed to appeal to Christians, but also to Buddhists, Zoroastrians, followers of the Mithraic Mysteries, and Hermes-worshippers among the Levantine Pagan religions which later became extinct), and also indigenous heathen religions (which actually copied practices from the Assyrians, for example, the Tibetan Buddhist hierarchy and their system of chant appears to be derived from that of the Assyrian Church of the East, and likewise the Taoists in China began copying the layout of Assyrian Christian altars, with two lamps on each end of the altar, in a rectangular shape, often against a wall, and the offering placed in the center (albeit in the case of Taoists, this is an offering to the Immortals, the Jade Emperor and various figures from the pantheon of Traditional Chinese Folk Religion, which Taoist priests tend to administer, and also the canon of Taoist immortals such as Laozhi).
However within Christianity, size, while not everything, is important, since by maximizing the size of those denominations which practice the traditional liturgy, we can maximize adherence to the apostolic faith, and work to abolish innovations introduced by well-intentioned but grossly misguided Restorationists such as George Fox and Ellen White.
Among Restorationist churches, the only one which I think really did manage to restore something which had been lost by most Protestants was the Stone/Campbell movement, which led to a few different denominations such as the Churches of Christ with their lovely A Capella singing and the Christian Church/Disciples of Christ. The Stone/Campbell movement, with its emphasis on weekly reception of the Eucharist (which had also been stressed by John Wesley, but unfortunately most Methodist churches stopped celebrating the Eucharist weekly).
Of course, Stone and Campbell also made some mistakes, such as rejecting creeds as divisive, which just invites heterodoxy. The surest way of ensuring doctrinal Orthodoxy is to include the singing of the Nicene Creed and historic confessional canticles. I posted a list of those I recommend, and in fact use as my statement of faith, here:
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