The Sacrifice was fantastic, and brought a tear to my eye in a couple of places, but something that really stuck out to me (that I didn't expect) was how important it is for the player character to have a voice.
Not just in the literal "they can talk" sense (although that is a huge one), but in the sense that they have a personal view that they bring to the table, and one that contrasts the other characters, because of what they (and we the player) have seen and experienced in the game world.

The player character, The Operator, has a strong sense of agency, and makes decisions throughout the game's quests (usually with you, the player, actively making some of these choices), and that is something that DE has developed very well since the Operator was introduced. As I noted in the stream, when we are introduced to the Operator, they are in a literal sense, a quiet, helpless child.
Over the game's quests, as you, the player, become more and more aware of the world and how the Operator plays, they too are learning, so there is a connection between the two of you, where you get better and unlock more of their abilities and complete quests, and in turn they become more vocal. In this latest quest, our Operator has become one of the biggest badasses in the entire game, willing to go up against a wild Warframe single-handedly, ultimately becoming one with it, and taking down your greatest and oldest enemy, bringing their story arc to a great conclusion, and we, the player/Operator, have some of the best, most memorable, and hardest-hitting lines in the game.

Likewise, our Guardian should have had growth over the course of our time in Destiny. Instead, they simply accept that they are Guardians, and the only hints of personality are in the Reef cutscenes (and the "Little Light" quip). After which, they become completely mute, out of lazyness or misguided ideas about player-avatar immersion.
I wish our Guardians had had any sort of concern, or reservations, or fear. The Red War would have been a great avenue to explore all of that, and we could have had the Guardians react to being powerless, then gaining a brand new ability, and so on, until we finally stepped past our Vanguard leaders for a second round against Ghaul. It would have given our characters a depth that would make our connection more personal.

Boy would that have been great.

Anyway, I'll leave you with two great characters who have more depth in three quests than Bungie has given us in-game during the past four years...

I still lurk here and see you playing warframe so it was cool to see another post. Your giving me an itch to play again. Sorry i fell off the wagon a bit.

Also I love how Skillup brought up the Legacy of Cain SoulReaver Series. One of my favorite PS games that did have an awesome story that they successfully branched out into multiple game entries. Its definitely outdated and wouldn't hold up that great today, but man back in the day!