“And no man taketh this honor unto himself, but he that is called of God as was Aaron” (Hebrews 5:4).
How was Aaron called? By his brother Moses, the prophet, who then laid hands on his head and conferred the priesthood upon Aaron. Where did Moses get the authority? From Jethro, his father-in-law, a Semite, who held the Melchizedec priesthood (D&C 84:6-7).
And where do modern-day Christian ministers and leaders derive their priesthood authority? From schools, universities, and institutes. From a calling they feel deeply and sincerely. I do not question the sincerity of another’s belief, but God explained clearly the process of getting the priesthood, it must come from one who already has it.
There are only two churches on earth that claim a direct line of authority to the Savior, the Catholic Church and The Church of Jesus Christ of Latter-day Saints. All others churches either split off from one of these two or started their movement because someone felt called to the work. Having a wonderful and spiritual story does not convey the keys of the priesthood upon a person.
The field is narrowed from two to one when you consider the mode of baptism. It is by immersion. Isaiah warned of organizations who change the ordinances (Isaiah 24:5). The earth is defiled by such abominations. The difficulty lies is being the cause of defiling the earth and then claiming authority from God.