I don't think "this is how Bungie is" is a good excuse, though.
The problem with "Game first, story for those who want to look for it" is that Bungie themselves hailed the story as epic, cinematic, etc. blah blah blah. I think everyone agrees that, when it comes to delivery, they failed. If they wanted this game to be memorable for its story, they failed.
That is the #1 rebuttal to "this is how Bungie has always done it". Which is arguable, btw.
However, I DO agree that there IS a lot of interesting backstory and lore there...which makes it all the more disappointing that they failed to convey or communicate this to you unless you read the Grimoire OUTSIDE of the game.
It doesn't have to be one or the other--"game first and story second" is not a rule and it doesn't have to be one. When you visit the Ishtar Academy Library, your ghost says that losing this sacred source of knowledge to the Vex would be a huge blow. Why? He says that there is a lot of knowledge there, but in all actuality, in terms of gameplay, it's just a new stage to shoot bad guys in.
You're literally in a library that is said to be a crucial source of Golden Age knowledge--and that is the extent of it! You're not really told what that knowledge is, you can't read anything (despite being surrounded by thousands of books).
Instead, you just protect your ghost as he unlocks a vault.
I am having a good time in MP, but playing this game SP is frustrating as it is boring. I'm not rushing around with friends and can take my time, but there is no impetus to do so unless I want to find dead ghosts or loot chests.
/rant
Oh wow, I don't know why I didn't connect those references! Found any Marathon references?
Fun fact: my heart dies a little every time I read about the "Lords of the Fallen" game, as I always think it's a new Myth game