Mormons are still seen as heretics though and Joseph Smith is still seen as a false prophet in the eyes of most Christians.
The Mormons don't officially believe in the Trinity (a basic requirement for Christianity because you cannot have Christianity if you don't believe in the Trinity) as the Mormons believe that God, Jesus, and the Holy Spirit and three separate beings rather than one (this is sacrilegious heresy in the eyes of every Cristian ever that isn't a Mormon) and this technically makes Mormonism a polytheistic religion rather than monotheistic as seen with every other Christian denomination (even Christian denominations that don't adopt the Nicene creed like the Amish and Anabaptists they still believe in the Trinity because even they know you cannot be a Christian if you don't believe in the Trinity). So in a strange way, Mormonism has more in common with Hinduism than Christianity because Hinduism is a polytheistic religion and we see the Mormons believe in three separate beings instead of one.
Joseph Smith had failed prophecies with the most notable one with him claiming that a grandiose Mormon temple in Missouri would be built within generation that was alive in the year 1832 because Joseph Smith claimed God foretold this to him. What actually happened was that the Mormon temple that we know today was built in Salt Lake City, Utah instead. So did God changed his mind? Or could it be that Joseph Smith was a massive bullshitter. Hmm. There's still no overglorified Mormon temple in Missouri and the plot of land that was meant for this temple still remains empty to this day.
There was also Joseph Smith lying about his so called "Book of Abraham" where he used papyrus scrolls from the Egyptian 'Book of the Dead' to make the claim that he discovered a "lost book" written by Abraham when in reality it was funerary texts written by the ancient Egyptians and we know they're funerary texts because actual archeologists discovered the Rosetta stone which allowed humanity to rediscover ancient Egyptian (as the Rosetta stone was used to translate Egyptian hieroglyphs into ancient Greek which can be translated into English and other modern day languages) and we deciphered these hieroglyphs using what we knew from the Rosetta stone to show that the so-called "Book of Abraham" had nothing to do with the Bible and they were just instructions for ancient Egyptians to bury their dead.
There is also Joseph Smith's well documented pedophilia because much like how Muhammad married Aisha when she was six years old and had sex with her when she was nine years of age according to the story of Islam, here we see Joseph Smith would do the same thing where he married several prepubescent girls at the time and this is public record (there's a reason why many people call Mormonism as 'White Islam').
I'll say this. The Mormons that I've meet are actually pretty nice people (yeah I've meet my share of douchebag and judgmental Mormons here and there but this isn't enough to convince me to see Mormons as horrible people because I have a pretty positive experience when talking to Mormons in general). Even with that said, Mormonism is a dying religion because many younger members of the Mormon church end up discovering the Internet and they start reading books about the history of Mormonism where they realize that Joseph Smith was a horrible person and the Mormon church feeds bullshit to people so said younger members of the Mormon church just end up leave the church where they either become atheist/agnostic or they convert to a more respectable branch of Christianity that doesn't preach heresy (Catholicism, Orthodox Christianity, Lutheranism, Baptist, Methodism, etc).
I can go on about why Mormonism is bullshit but the only thing I can say is that Mormons are generally nice people (at least on the surface because I don't know what really goes on behind closed doors with Mormons) but them being generally nice and pleasant to be around doesn't excuse Mormonism itself being just as retarded as Scientology.