The Mormon Church has claims since its earliest days to be a restoration of an "original" Christian religion. The 9th Article of Faith states, "We believe in the same organization that existed in the Primitive Church, namely, apostles, prophets, pastors, teachers, evangelists, and so forth."
However, the era of modern biblical studies arose a few decades before the Mormon Church began, and it's rapid pace of study and learning has continue ever since. The ability to read the Christian New Testament as a unified work has grown extremely tenuous. The formation of Christian orthodoxy and its various hierarchies is now seen as a very organic process that took decades and centuries.
As such, past arguments to "prove" Mormonism as "primitive"