Your argument is with SLC, that’s what they’ve said from the beginning.
“Complete apostasy”.
Now you are attempting to segue into “...not one whit of gospel truth...”. That’s mormon doubletalk, backing off of their original assertion. Not buying it.
B.H. Roberts, an LDS Seventy and LDS Church historian, in his introduction to the History of the Church, stated that the LDS Church is founded upon this very premise. He wrote, “Nothing less than a complete apostasy from the Christian religion would warrant the establishment of the Church of Jesus Christ of Latter-day Saints” (vol. 1:XL).
How could there have been a total apostasy of the church since Jesus promised that “the gates of hell shall not prevail against it”? (Matt. 16:18) Jesus also promised, “lo, I am with you always, even unto the end of the world.” (Matt. 28:20) There couldn’t have been unless Jesus lied.
Another problem with the LDS claim of a total apostasy is their own teaching that John, one of Christ’s twelve apostles, did not die (see D&C 7:1-3) but was to remain on the earth to “prophesy before nations.” Besides John, three of the twelve disciples in the Book of Mormon were granted their desire to remain on earth, to “bring the souls of men unto me,” until Christ’s return (Book of Mormon, 3 Nephi 28:6-9).
With four apostles remaining on the earth, how could there have been a total apostasy? The only obvious answer, is there wasn’t one.
SLC perpetuates a lie of their own making.
Jesus promised that “the gates of hell shall not prevail against it”? (Matt. 16:18) Jesus also promised, “lo, I am with you always, even unto the end of the world.” (Matt. 28:20) There couldn’t have been unless Jesus lied.
Jesus cannot lie or else he wouldn't be God. So we agree on that.
Matt. 16:18 is best translated that “the gates of [Hades] shall not prevail against it.” Hades being the holding place for dead spirits. This is in keeping with the OT Sheol and with LDS doctrine as regards the dead, no?
It actually makes the most sense when you think about the LDS doctrine of work for the dead. In this context it's obvious that Jesus meant his Atonement was infinite and could not be limited even by death.
For Matthew 28:20 context matters. A common tactic of eisegesis is to snip a verse, taking it out of context and then buttressing your doctrine by it, but that's just putting too much sand in the mix and castles built of sand...
The verse only makes sense as a complete thought and Jesus' thought is (Matt. 28:19-20):
"Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age."(I used the NIV as it is pretty close to the actual Greek)
The "make disciples" is mathéteuó and means "helping someone to progressively learn the Word of God to become a matured, growing disciple (literally, "a learner," a true Christ-follower); to train (develop) in the truths of Scripture and the lifestyle required, i.e. helping a believer learn to be a disciple of Christ in belief and practice.
Baptizing is baptizó meaning properly, "submerge" (Souter); hence, baptize, to immerse (literally, "dip under"). 907 (baptízō) implies submersion ("immersion"), in contrast to 472 /antéxomai ("sprinkle").
"Teaching them to obey everything I have commanded you" is very interesting and you'd profit by grabbing your Strong's and reading the Greek with the definitions. I like going here Matthew 28:20. I hate relying on anyone else's interpretation as you're likely to be mislead. There's so much eisegesis out there it isn't funny.
So only under the preceding circumstances does Christ promise, "And surely I am with you always, to the very end of the age," function.
Once you lose authority to preach, baptize and teach "all that I [Jesus Christ] have commanded you" you most certainly have apostasy and it sounds complete.
Total apostasy can still exist under these circumstances, no? Imagine we'd taken apart a motorcycle down to its constituent parts. Some would have a tire, a spark plug, gas tank, etc. It wouldn't be a motorcycle even though all the parts are there.
You'd still have complete apostasy even with these four still alive, no? The only exception would be if they were still discipling, baptizing and teaching the commandments of God.
Do the LDS believe they were doing that at the time of Joseph Smith's vision?