Examning your specific choice of words more closely:
The Church of Jesus Christ of Latter-day Saints does indeed teach the Book of Mormon,
I agree. I said it does not follow the Book of Mormon
and the Book of Mormon doesn’t teach that Jesus is “all that matters” …
Note that you further qualify this statement with an assumption. As an unqualified statement, the Book of Mormon does teach that Jesus is all that matters
… in the sense that this would mean there is not a need for prophets and apostles in the midst of also believing in personal revelation such as the vision of the tree of life that both Lehi and Nephi received.
This constitutes your assumption: The belief in personal revelation is actually inherent to Christianity.
Prophets and apostles are called of God to lead people to Christ through their teachings and example. They also are able, by revelation and by visiting places throughout the world, to discern when there is a need for warning or
Apostles/Prophets or Popes/Bishops, the name matters less than the role. Their purpose is to keep the Body of Christ on course toward actualizing Christ in our lives – they do not supercede our personal relationship with Christ, they reinforce it, and that is what should be most important to them. We acknowledge our Ecclesiastical leaders (whether you as a Mormon or myself as a Catholic) because we perceive them as more fully succeeding in putting Christ first in their lives, therefore, Jesus is still what it is all about, and all that matters.
when there is a need for helping the people in a particular place who may have brought some ceremony into their practices that represents a change from the simplicity of the gospel, and needs to be changed back to that simplicity.

What is so simple about Mormonism? The Church of Jesus Christ of Latter-day Saints cannot even assert its claim to authority without delineating feats of historic gymnastics to refute existing claims. You do not even consider baptism permanent, as those excommunicated get rebaptized when they repent
(a very sacrilegous concept to Catholics, rebaptism: Catholics are so committed to the idea of “one baptism” that almost any denomination’s baptism is considered valid, and converts already baptized are merely confirmed as Catholics – The Holy See takes great care in deciding whether or not to acknowledge a baptism as valid, and did not rule on Mormon baptism until 2001)
Confession can be a complex process involving more than a dozen people hearing it, and later any of them could just be regular members of the congregation. The LDS Plan of salvation requires a complex flowchart.
Try this for simple: God created everything out of nothing. He created men, who failed to trust him and lost communion with Him. He so desired this to be restored that He reached out through time and as men responded favorably to him he drew them closer, until in Christ He revealed himself fully, and left the Church to hold his followers together, and the Eucharist to change their nature. You are created when you are conceived. Baptism makes you a child of god, and Confirmation affirms your commitment to your baptism. You remain in communion with the Body of Christ, the Church, through the Eucharist, and repentance and forgiveness becomes part of an ongoing process, as you continually reconcile yourself through confession. When you die there is immediate judgment over whether you are bound for heaven or hell. If you are bound for heaven but not ready to go, there is a waiting period for more purification.
This all depends on the Grace of God, and the Grace of God is sufficient to cover things like Children who die without baptism, or people who live their whole life without it but still have souls dedicated to truth.
That is pretty simple. Many LDS doctrines that came in after the Book of Mormon complicate things so as to diminish the grace of God.
But certainly a person is better off believing in Christ than not believing in Him at all, so long as this leads to repentance and forgiveness and love of others, and He is central to the plan of salvation as taught in the Book of Mormon
and the Plan of salvation as taught in the Book of Mormon is not completely consistent with the plan of salvation as taught by the LDS Church. Take my challeng, and just read the Book of Mormon as an independent book.
as well as in the New Testament. Those doctrines do matter most in the gospel, and are only possible through Him in their fullest expression.
First, their fullest expression is in the Eucharist. What you call the sacrament was never intended as a mere symbol, according to the New Testament. The question is, if the authority was never removed from Earth, what need is there for any testimony other than the New Testament. When was the authority removed from Earth?