Exodus 29 :44-46 (KJV)
44 And I will sanctify the tabernacle of the congregation, and the altar: I will sanctify also both Aaron and his sons, to minister to me in the priest’s office.
45...
Book Of Mormon Contradiction: Mosiah 18:17,18
The importance of priests was to administer in the tabernacle. Those days ended with Jesus and Him setting up His church.