John 3:16 isn't Mormonism. Neither is Romans 1:16.
Mormons claim that all churches other than their own are wrong, that the Gospel is only in Christ's church, and that The Church of Jesus Christ of Latter-day Saints is the only church with which Christ is pleased. Joseph Smith claimed that all other churches "teach for doctrines the commandments of men." Mormons also teach that
only they have authority to baptize.
1 Nephi 14
9 And it came to pass that he said unto me: Look, and behold that great and abominable church, which is the mother of abominations, whose founder is the
devil.
10 And he said unto me: Behold there are save two churches only; the one is the church of the Lamb of God, and the other is the church of the devil; wherefore, whoso belongeth not to the church of the Lamb of God belongeth to that great church, which is the mother of abominations; and she is the whore of all the earth.
Doctrine and Covenants 1
30 And also those to whom these commandments were given, might have power to lay the foundation of this church, and to bring it forth out of obscurity and out of darkness, the only true and living church upon the face of the whole earth, with which I, the Lord, am well pleased, speaking unto the church collectively and not individually—
31 For I the Lord cannot look upon
sin with the least degree of allowance;