"Catholicism is Christian; Mormonism only claims to be."
The whole protestant thingie was because some folks thought Catholicism was not doing it right, either. Remember?
Not doing it right and an almost completely different religion are 2 different things.
I think there will be plenty of Catholics in Heaven, and I suspect plenty of Mormons - it just depends on whether they put their faith in Jesus Christ or some man-made salvation. (not a judgment of anyone, just an opinion)
Not too surprising to me that there are many schisms in Christianity - the Bible is a complex Work subject to interpretation, both good and bad. Again, the important thing isn't which 'schism' you're following, but in Whom you place your faith.