I came to the realization that I kinda dislike over-saturated lore in general. It makes some franchises so difficult to follow, and it creates these creepy know-it-all superfans that get livid if you get the tiniest detail wrong when talking about a movie or game. This is what happened with Star Wars, and it's happening with Halo, too.
Hurts, bruh. :( I thought we were friends.
But I kind of see where you're coming from. It does make it hard to get into an established franchise, I suppose. Doesn't help when the books have some crucial setting-building that the games lack (Halo The Fall of Reach to Halo CE) but at the same time, they're useful tools for establishing new characters.
Fireteam Osiris in H5, for example, have used a bunch of stuff in te past year; Nightfall (Live action web series), Hunters in the Dark (Novel), Escalation (Comics) have been used to introduce three members of the squad (Buck was already in another game) so that more time in game can be spent on the actual storyline. They did the same with Forward Unto Dawn (webseries) and Initiation (even though it was shit).