That final celebration scene is the most bizarre thing. I didn't really understand what was being celebrated. I destroyed some black heart thing that didn't seem like a big deal (just another inconsequential boss in the long succession of boss things to kill), then people were super happy. Way more happy then they were about all my previous efforts. It feels like Bungie playtested the final sequence, was given the response of 'that doesn't feel like an ending,' then haphazardly threw together the most inoffensive and generic closing to a piece of action-oriented narrative.
Now excuse me while I log into bungie.net to see if I can fumble around with these dumb cards to contextualize why I shot some robot things a bunch of times.