What you fail to realize is that Destiny and its Grimoire is the pinnacle of Bungie's storytelling ability. We saw flashes of their brilliance in their previous works. In Halo 3, the plot is nowhere to be seen until halfway through the game. With Halo: Reach, they did the bold move of disregarding and retconning the hell out of all previous lore regarding the Fall of Reach. With Destiny, they have truly innovated by discarding the unnecessary story and requiring players to go to an outside source.