You don't need a fax when one has the Holy Ghost!
The Lord gave his Doctrine and Covenants all through history on earth.
We Have a Benchmark in the Bible to bring all knowledge there...ponder, pray and let the Holy Spirit teach our minds that which is of the Lord!
But it really comes down to a matter of faith. Either the Elders got it right, or they didn't.
There's no way to know objectively. I think they may have gotten most of it right. I have serious doubts about Revelation. It's goofy and it's caused major heartache among believers who think they've somehow unraveled veiled prophecies.
None of which matter to any individual in the overall scheme of things, anyway...