At the time of the Reformation, the Catholic Church was corrupt. They used their spiritual power in political ways, such as overthrowing nations, expanding land holdings with soldiers, and excommunicating kings along with all of their subjects. They were also doing things such as withholding half the sacrament from the people (giving them only the bread), not teaching about faith as a principle, and selling indulgences (basically allowing people to "buy repentance" for some sins). Their focus was on their 7 sacraments (basically their version of saving ordinances) that they taught only came through the church. Without those, they taught the people would be damned. With them, they taught the people would be saved.
Their main flaw was teaching that receiving the ordinances from the church was enough to save people.
Now enter the Reformation. Many individuals saw the abuses of the Catholic Church, and that changes were needed. Martin Luther tried to point out the problems and get the church to reform, but it excommunicated him instead. So now he was on his own. He didn't have any keys (in all honesty, neither did the Catholic Church), but he knew that baptism was still required. What was he going to do now? His solution seemed to be to make everything contingent on faith. The people would still baptize, even without authority, relying on God to give them authority because of their faith.
Their main flaw was teaching that, if they just had enough faith, it would overcome the lack of keys and that God would honor the ordinances anyway -- here, and in the next life.
Eventually, though, we got the Restoration. With it, God put everything back into its proper place. It wasn't an either/or problem -- faith or works. The solution was not either/or but and -- we need both faith and works -- both principles and ordinances. I think Joseph Smith makes this very clear in the Articles of Faith 4-6.
Faith and works together. Principles and ordinances both required for salvation. Faith, repentance, baptism, and the gift of the Holy Ghost.4 We believe that the first principles and ordinances of the Gospel are: first, Faith in the Lord Jesus Christ; second, Repentance; third, Baptism by immersion for the remission of sins; fourth, Laying on of hands for the gift of the Holy Ghost.
To administer in the ordinances, you need laying on of hands by those who are in authority (meaning who have the keys).5 We believe that a man must be called of God, by prophecy, and by the laying on of hands by those who are in authority, to preach the Gospel and administer in the ordinances thereof.
This organization is all about getting both keys and truth down to the people so they can be taught and receive saving ordinances in all parts of the world.6 We believe in the same organization that existed in the Primitive Church, namely, apostles, prophets, pastors, teachers, evangelists, and so forth.
In summation:
If your argument is that ordinances (with keys) are all that are required for salvation, you are wrong.
If your argument is that you need no keys at all, but faith will make up the difference for salvation, you are wrong.
The answer is that both are needed.
I believe that the life of Jesus Christ shows this very plainly. Although he lived a sinless life, He still needed to be baptized by one who held the priesthood keys.
I hope this helps at least a little bit.
