Kishkumen's statement is true in the sense that no human can provide the all the benefits to all promises made. It is true, that humans cannot always deliver. God, on the other hand, can deliver. He is omniscient and omnipotent. We are not. Therefore, only God can reliably be trusted to deliver on His promises. As members of the church we believe that the covenants made with God result in promises made, promises kept. And the conditions under which blessings are predicated.
I'm referring to the God of Abraham, Isaac, and Jacob. As members of the church we believe it is that same God that speaks to prophets in the Book of Mormon. The promises of spiritual knowledge, divine help, and salvation are tied to that specific deity.
The Creator of Heaven and Earth. The Big Guy (His Son, anyway)...but He's a God too.
This is a faith, an act of belief. That faith and belief cannot be "justified" and/or proved to a non-believer. We will ultimately reach an impasse.
Regards,
MG