The church is necessary to teach the Gospel, since the Gospel would die out or get mutated without an organizational structure to promote it. Of course, the Gospel gets mutated even with churches teaching it, but I still see organized religion as necessary to preserve teachings. It’s the Mulekite principle, whether that story is historically accurate or not.
Also, the teaching of systematic theology is dependent on churches – with the good and bad that occurs through that systematization.
Finally, for many people (the large majority, I would argue), community in all its iterations is necessary to be and feel fully human. Church (organized religion) plays a vital role in that part of being fully human.
Specific to the LDS Church, it is necessary to teach LDS-specific ideas – some of which I absolutely love and that might not exist, especially within Christianity, without it. There really are some uniquely Mormon concepts that I think the world is better for having, even if there are more that are shared to varying degrees and some that I hope are pruned from our vineyard.