This would be a valid and interesting point if you first assume that the Church already has and understands all of the truth from God and that God cannot, will not or is uninterested in continuing to speak to His children and given them counsel, advice and direction. In short, these accusations only make sense if you deny the principle of continuing revelation, which is a foundational principle of LDS doctrine. While we do affirm that the invariance of the truth from God, that invariance does not make Him immutable or merely muted. We believe in continuing revelation from God, and that God had guided, counseled and commanded His children, and that He does so today, and will continue to do so, "For do we not read that God is the same yesterday, today, and forever, and in him there is no variableness neither shadow of changing? And now, if ye have imagined up unto yourselves a god who doth vary, and in whom there is shadow of changing, then have ye imagined up unto yourselves a god who is not a God of miracles." (Mormon 9:9-10)
Some would use this verse and others like it to make God immutable and dumb, but in doing so they would deny current, and future (and by extension, past) revelation. By arguing that the the Church cannot have current revelation and direction, is to argue that the doctrine, as taught by Joseph Smith, was whole and complete in the first instance, and that nothing could ever be added to it, by way of clarification, extension, and further commandments to aid us in our lives. That is, to deny continuing revelation is to deny that God is interested and invested in who we are and what we are doing. It is to imagine up a disinterested God that does not care about His children, despite the assurances given that, "the mountains shall depart and the hills be removed, but my kindness shall not depart from thee, neither shall the covenant of my peace be removed, saith the Lord that hath mercy on thee."(3 Nephi 22:10)
To finish I will include part of an article written by President James E. Faust about continuing revelation. (James E. Faust, “Continuing Revelation,”Ensign, Aug 1996, 2)
The responsibility for determining the divine validity of that which one of the oracles of God may state does not rest solely upon him. President J. Reuben Clark, formerly a member of the First Presidency, stated, “We can tell when the speakers are ‘moved upon by the Holy Ghost’ only when we, ourselves, are ‘moved upon by the Holy Ghost’ ” (J. Reuben Clark: Selected Papers, ed. David H. Yarn Jr. , 95–96). This is in harmony with the counsel of President Brigham Young:
“I am more afraid that this people have so much confidence in their leaders that they will not inquire for themselves of God whether they are led by him. I am fearful they settle down in a state of blind self-security, trusting their eternal destiny in the hands of their leaders with a reckless confidence that in itself would thwart the purposes of God in their salvation, and weaken that influence they could give to their leaders, did they know for themselves, by the revelations of Jesus, that they are led in the right way. Let every man and woman know, by the whispering of the Spirit of God to themselves, whether their leaders are walking in the path the Lord dictates, or not” (Discourses of Brigham Young, sel. John A. Widtsoe , 135).
Revelation was required to establish this Church. Revelation has brought it from its humble beginnings to its present course. Revelation has come like flowing, living water. Continuing revelation will lead it forward to the windup scene. But as President Clark told us, we do not need more or different prophets. We need more people with “a listening ear” (in Conference Report, Oct. 1948, 82).
We make no claim of individual infallibility or perfection as the prophets, seers, and revelators. Yet I humbly state that I have sat in the company of these men and I believe their greatest desire is to know and do the will of our Heavenly Father. Those who sit in the highest councils of this Church and have participated therein as inspiration has come and decisions have been reached know that this light and truth is beyond human intelligence and reasoning. These deep, divine impressions have come as the dews from heaven and settled upon them individually and collectively. So inspired, we can go forward in complete unity and accord.
I witness humbly that I know the Lord guides His Church through His servants. I know them to be noble, righteous, dedicated servants of the Lord. I pray that we may be responsive to His Spirit and be found listening to the oracles He has appointed. I so pray because I know that we mortals, without the aid of revelation, cannot know the purposes of God.