Religions never spring to life fully-formed and without any connection to the religious and cultural ideas around them. (Scientology is the nearest to an exception I can think of, but it claims not to be a religion. It is heavily indebted to 1950s science fiction, anyway.)
Sometimes a “new religion” is like the Lutherans, more of a family squabble about reform than a whole new religion. “The Bible should be translated into the local language so everyone can read it.” “No, it should stay in Latin, because we’re Romans, remember?” And so on.
The angel "Moroni" giving Joseph Smith the "golden plates" in "Reformed Egyptian"
But sometimes you get a kid with a streak of the con artist, writing screeds of bad fantasy in an imitative style…
Joseph Smith’s impoverished farming parents tried to make extra money by treasure-digging, and the teenage Joseph claimed he could use “seer stones” for this. He would put a special stone in a white stovepipe hat, and then see the information he needed in the reflections inside the hat. (At age 20 he was tried in New York state on the charge of “glass-looking,” or pretending to find lost treasure.)
In his teens he claimed to have been visited at night by an angel named Moroni, who revealed the location of a buried book of golden plates as well as other artifacts, including a breastplate and a set of silver spectacles with lenses composed of seer stones, which had been hidden in a hill near his home. Smith said he attempted to remove the plates the next morning but was unsuccessful because the angel prevented him.
A couple of years later he got hold of the golden plates, which the angel told him not to show to anyone, but to translate from the “Reformed Egyptian” and publish. They told the story of the Lost Tribes of Israel coming to North America and having all sorts of pseudo-Biblical events in pseudo-Biblical language, full of anachronisms like elephants, steel and silk; and then of Jesus appearing to these North Americans and essentially preparing for Americans (at least the believing ones) to be God’s Chosen People.
He subsequently translated other pages of Egyptian hieroglyphics (which no one else could in the 1840s) and determined that they were all about sacrifices and God and Abraham and so on. Unfortunately the pages have since resurfaced, and real translation shows them to be about embalming and funerary rites and Osiris. There is a Christian critique of the issue here.
So this “new religion” is not a simple reform like Lutheranism. This is one individual’s fantasy, springboarding off the Bible into whatever sounds good and will win converts. It’s not surprising that regular Christian sects don’t have much use for Mormonism – and that’s even before we get into Joseph Smith’s 34 wives, and the issue of everybody being able to evolve through several Heavens into becoming a God of their own planet, and all that jazz.
The irony is that from the point of view of Judaism, Jesus looks like a kind of argumentative reformist Luther… but St Paul’s Christianity, the Christianity that we have today, looks a hell of a lot more like Joseph Smith’s made-up Mormonism.