This will be my version of a critique that I'd like to get off my chest. Some part of me hopes Bungie will read it and bend Destiny to my desires, but mostly I'm interested in writing it down and seeing what people think.

Little Disclaimer
I'm not a writer, I've never stayed in a Holiday Inn. I believe that the Grimoire should exist to enhance a story, not to correct or make a story. Thus, everything that follows is my person feelings about the world as it exists without the Grimoire. Oh yeah, and it's a little disorganized.

World Creating
My favorite stories, regardless of medium, are those that create a world. In order to create a realistic world, you must impart to the reader/audience/player that there are things they don't know, there are mysteries out there they may or may not solve.

Two of my favorite worlds of all time are those of The Lord of the Rings, and Dune. Both worlds convey a sense of a large amount of mystery and power "out there" that you should be weary of. They don't bother to explain everything (at least not until way into the story), and they certainly don't beat you over the head with it. Instead you are forced to explore, ponder, wonder, and connect the dots to figure out what is out there. You might even have to use your imagination.

A good world doesn't even require a good story, or a complete story. I play devil's advocate around here a lot because I beleive the Destiny story isn't finished, and that there is hope for the story. It would be like reading the The Fellowship of the Ring (the 1st book) and stopping. You'd have a sucky story, something that amounted to a walk in the woods. However after the first book you have a sense that there is a large world, with lots of power, most of it hiding, and not all of which has picked a side yet. The stage is set.

Where I believe world builders often fail (at least in written form) is when they try and give too much detail. They try and put it all in a nice understandable neat box with a bow, instead of the messy and confusing pandoras box that the reality we live in actually is. This is however not what the Destiny world suffers from.

Bungie's World
I think this is what Bungie tried to do, they tried to start a bunch of threads that over time they could unravel at will, or leave open for the mystery of it all. Yet instead of failing in the traditional way, I think they left too much out of the world. I don't think they opened enough up. The story need not be good or complete at this point, but I think the world of Destiny needs to be. A complete world gives an emotional context to the little stories you tell.

Your ghost gives you lots of things to wonder about, lots of threads that could be pulled, but I feel your Ghost never goes far enough. Take this for example:
"Humans haven't set foot on the moon in hundreds of years" leaves a question open, that's a thread, but it's not a thread with much gravity yet. It doesn't convey the importance of the situation. Did we stop going because Guardians are allergic to moon dust? Purely because of Tower leadership philosophical disagreement? Or because something we don't understand killed a thousand* guardians and we really aren't sure if it's still there or not?

The Chess Piece Analogy
The book Dune is famous for conveying 1/10 of 10 different plots. Everything is plots within plots. You can not read that book hoping to understand everything you read. You are not meant to understand the motives of the different players until the end, or more likely until you've read it a 3rd time. But there is never a doubt that, despite how much or how little you know about the different entities, that they ARE players in the game. They may not be the Queen, but they are certainly a Rook.

How to Identify a Chess Piece
The primary dialog does convey to us that there are these things out there that we don't understand or know. Some are clear enemies, some are friendly, and others are neutral or hostile. But few have been given the sort of power (either through myth or evidence) for us to really be concerned with. And very few are given much respect by the entities we trust and know to be powerful, e.g. The Speaker, out fellow powerful Guardians, or our enemy.

Oh, We Do Have A Chess Piece
The primary exception to my complaint above are the Outcast. The cut scene played as we approach the Reef in a ship speaks wonders to the mystery and power of the Outcast. They openly oppose any ship that approaches them? That means they aren't really hiding, and in fact their demeanor is one of cocky arrogance. We can surmise that The Fallen rarely mess with them, or if they do they make deals with them. The Fallen thus respect them for some reason. That alone says that we as the Tower should be interested in knowing more about them, so as to figure out if they are friend or foe. They are an obvious sleeping giant, a piece worthy of being on the board. And none of that requires a story, none of it requires answers.

Not a Chess Piece
Contrast that with that Exo that never has any time to talk. All I get from her is that she might be as combat worthy as a Guardian...maybe. She does a lot of running for someone that we're supposed to respect. She has nothing we desire except maybe a longer range teleportation and a form of cloak, but that's it afaik. She's a non-entity. I could get a report that the Exo died to a Cabal patrol and I've have to say "So what?". She promised nothing as a friend or foe, she gave no indication that she was a major player in the battle to come. She wasn't on the chess board. And worse than not being on it, she visits you at the tower, which means that the Tower acknowledges her presence and doesn't bother to say anything about it. This only emphasizes the idea that she's a non-entity. I want to care that she's in the story, but I don't know why.

This same thing goes for the Nine. It was only recently that I found a scrap of a clue that the Nine might be relevant to my universe, and half the reason it's good info is because of where it comes from.
"If only the Nine would help." - The Speaker
That's someone that we respect telling us to respect the Nine. That's the speaker telling us the Nine are on the chess board, they are players. But that line is buried as something the speaker-as-a-vendor says, and we have little reason to hang out around him. And as something he mumbles to himself it really doesn't have the same oomph! that we need.

Besides a snippet from the Speaker, we are left with myths about the Nine so ambiguous that the best we can say is that they probably aren't a bunch of stay-at-home-parents that got scared, bought a ship, and took off to hide behind one of Jupiter's moons. There is little indication that they are anything but scared, dead, or simple merchants. They seek to interact but only indirectly and through trade.

I'm Not Asking For Answers
While I absolutely do not want Bungie to explain all of these entities, I do want them to put more information front and center so that we get the sense that there are sleeping giants out there that if woken will, for good or bad, have an impact on our solar system. Think Ents in TLOTR. I want to both fear and desire to run into them in the Universe, I want to care about them and their motives. I want to suspect that I'm not the biggest badass in the universe, and right now I think that.

And how about all the Guardians that may or may not be a part of the Vangard? Are we ever lead to believe that there are Guardians out there like Eris? Ones out there like Toland that we should be cautious if we bump into? I don't think we are. In TLOTR and Dune we start with the myths of Elves and Fremen, and then we are quickly given little examples that give the myths plausibility.

What I wouldn't give to run a mission where off in the distance you see a Guardian that you assume is just like you, only to watch them obliterate the enemy with an ability we've never seen, and then have them vanish before we can catch up to them. How powerful of an open mystery would that be? Would that not
A) Scare you a little
B) Cause you to seek out answers

How many Grimoire cards would that bring to life if you experienced it? How much more anticipation would that bring?

Thoughts On The Grimoire
The Grimoire is great for filling in detail, bringing characters to life, but it does a poor job of building suspense. Do you know when I found out we lost a thousand guardians on the moon? AFTER I played through every moon mission, and spent a lot of time there feeling not threatened. The first time I heard Eris talk about how scary the moon is my gut reaction was "Pansy, the moon is nothing". The Grimoire should promote and multiply the feelings they game has already solidly conveyed.

Other actors in the story such as the The Traveler have been given solid respect and fear without revealing their mystery. Same goes for Rasputin, but only after the expansion. Prior to the expansion and reading the Grimoire, I thought Rasputin was an annoying** AI, not a possible HAL figure.

There, I feel so much better having written that down :)

TL;DR
Books may screw up world building by beating you over the head with answers to every question they ask, but Bungie swung too far in the opposite direction by rarely asking the questions, and never providing front and center the gravity of the situation. I do not fear, respect, or desire to meet any of the other entities, because I do not believe them to be main players in my struggle against the darkness.

*Speaking of a thousand, is that a significant number of Guardians? How many do we have left, 100,000 Guardians or 100? If you ask me, I've only ever counted 16 including myself.

**Actually that's not entirely true. I did fear him, but only because he is an AI in a Bungie game, and those mother huggers are always causing trouble.