@Prayer Warrior , I'm going to go over one example of clarifying actual LDS Christians beliefs and sorting that from bad information. To facilitate this and cross any communication hurdles, I'll be using Protestant lingo unless otherwise noted.
The point I'll be talking about first is this:
The above quoted section is mixing up several different definitions of "church" and hence trying to compare apples and puppies. I'll talk about each definition and then compare beliefs on each point.
1) "Church" being the body of saved believers (the "invisible church", to use Protestant lingo): Protestant Christians, LDS Christians and vast vast majority of all other Christians do believe Christ being a member of the church is about welcoming Christ into your heart, accepting Him as your Lord and Savior, and following Him. This is the thing that matters most, above all others.
LDS Christians readily acknowledge that there are individuals belonging to this church in non-LDS pews: that many people sitting in Protestant pews, Catholic pews, LDS pews etc belong to this church and will spending eternity dancing with God. Conversely, there are some individuals sitting in LDS pews that are only giving lip service to God and their hearts are set elseware.
Both LDS Christians and other Christians believe all of the Bible verses quoted 100%.
2) The ultimate True theology: needless to say that there is one ultimate theological Truth from God. In Heaven we're not going to be having all of the theological debates like we see on this forum-- we'll know all of the Truth all of the way. And there is only one ultimate theological truth. In the mean time we're all still learning. Theology is super important, even if it's not what saves a person.
3) "Church" being the visible church - a literal on Earth organized group where Truths are preached: traditionally Christians did indeed believe in the importance of this. Catholic and Orthodox churches being millennium old examples of that belief. Protestants are more varied on this importance of literally going to church or organization beyond the local congregation. LDS Christians do believe in the importance of a literal organized visible church.
It is to that definition the quotes from "Joseph Smith — History 1:19" and "D&C 1:30" are referring to. That doesn't mean that individuals are perfect (cause they ain't remotely!).
Using a specific example to further illustrate this: using definition #1, I (and other LDS Christians) readily acknowledge the salvation of a Catholic person and we are in the same church. Using definition #2: I don't believe that everything Catholicism teaches is the ultimate Truth. They have many good things taught therein, but I have some serious objections on certain points. Using definition #3: obviously I don't believe that the Roman Catholic Church is the primary literal vessel in which God is primarily doing His work, even imperfectly.