1. Sometime in our future (the game's past), a large white sphere called The Traveler comes to Earth from the depths of space.  It elevates humanity to new levels of understanding, enabling us to begin exploring the stars in earnest.
2. The Traveler's sworn enemies, aliens called the Fallen (from where did they fall?), come to our solar system and start wiping everybody and everything off the face of the planets inhabited by humans.  The Traveler is weakened and, in its dormant state, can only protect one last human city on Earth (called the Tower).
3. Little flying robots called Ghosts work for the Traveler.  They resurrect dead people to become Guardians and fight the Fallen.  In the Tower, there is a man who speaks for the Traveller, but he's all cryptic about what the Traveler actually wants because every good sci-fi/fantasy story needs an enigmatic guy in mystic robes calling the shots.
4. Each Ghost is assigned to a Guardian.  My Ghost seems to have resurrected dead people before to fight for the Traveler, but those folks died again in battle.  My Ghost hopes this time will be different.  When I die, I'm resurrected again.  My Ghost must've given up on his previous charges after they died one too many times or perhaps I'm just that likeable. 
5. After shooting at the Fallen for a while on Earth, I steal a basic spaceship and am told I need to go to the moon.
6. The Hive live on the moon.  I'm not sure where they originally come from, but they've made themselves right at home in and around a big place they've built called the Temple of Crota in which is kept the legendary Guardian-killing Sword of Crota.  Some of the dialogue suggests the Hive wish to resurrect Crota him/her/itself who will probably be pissed that people have been using his sword and set up shop in his temple in his absence.  Wouldn't you be mad if you came home after being away for a long time and found someone else playing your video games while laying on your couch? 
7. On the moon, I recover the Sword of Crota and use it to hack up the Hive.  After using it, the Sword vanishes.  Crota stays dead.
8. I'm told that I need to go to Venus.  I'm not quite sure exactly why I have to do this, but once I arrive I find that the whole place is overrun with a killer robot menace called the Vex that are basically Terminator robots in full Skynet mode.  There's something called a Vex Warmind and it is not a pleasant cyberintelligence. 
9. The Vex originate in a place called the Black Garden, but one does not just fly into the Black Garden without running errands first.  This information is offered up by the queen in the reef at a nearby asteroid belt, although exactly what she's queen of is not clear to me.  She does have an overbearing brother marching around barking orders like he's Mr. Bigshot though.  As a test of strength or perhaps because they're just screwing with me, the Queen and her brother order me to retrieve the eye of a Vex Gate Lord.  If I can deliver it, they'll tell me how to get to the garden.
10. The expository characters begin throwing around more and more proper nouns without fair context, telling me that I need to go assassinate the Winter Kell without explaining what the hell that means.  Sword of Crota, Winter Kell, Vex Warmind... maybe this is some sort of Game of Thrones madlibs.
11. The Vex send reinforcements to Venus via large portals that connect though massive stone rings.  Perhaps this is all Stargate extended universe fan-fiction.
12. I storm the Vex headquarters on Venus and blast a Gate Lord into scrap.  I steal his big red Terminator eye and return it to the queen who tells me to take it to Mars.
13. I get my ass to Mars.  The planet is overrun with another type of alien, the Cabal, who are somehow even more furious than the Vex, Hive, or Fallen.  The Cabal are not happy to see me, but they're even less pleased to see the Vex who are currently trying to conquer them.  It feels good not to be the only person showing up uninvited to these things for once.
14. I shoot my way through Mars and eventually use the stolen eye to open a portal to the Black Garden which is located somewhere totally off the grid.  Eventually I reach the garden's heart and destroy it by blasting the three statues that it has brought to life using its advanced garden powers.
15. The Black Garden is destroyed, but this isn't a happy ending or even really much of any ending because Bungie has a ten year plan for this franchise and there are still two downloadable expansion packs to sell over the next few months, so in no way should I expect any kind of significant closure now.

How about it?  Am I close?  Despite my confusion, I had fun with Destiny and was better at it than I expected to be.  Since I've completed all there is to see until future expansions are released, I'm ready to send the game back to GameFly and move on to other things.  Perhaps when the complete edition of Destiny is inevitably released next holiday season with the DLC included, I'll consider coming back to play catch-up.  There's some great ideas in this game, but in my mind they all end up muddled together and I can't see beyond the broad strokes to the little details.  Destiny is far from the only game to have this problem; for instance, can anyone tell me from start to finish just what is happening in Assassin's Creed these days?  Maybe that's where Destiny excels.  Most franchises need multiple sequels to reach this level of confusion, but Destiny accomplished it in the course of a single release.  Now that is an achievement.