Fantastic breakdown, OP.
I think the main problem Bungie has with loot and RNG is they have so few items. Exotic, Legendaries and even blue and green items are so few that if it the loot system worked properly, everyone who's played the game for 20+ hours might have every piece of equipment there is.
Heck, just one look at Xur is evidence of this. He sells the same item week after week. Well, not exactly the same items but close. Bungie should have a team or something developing more Legendary, Exotic items to plug that hole.
In a way, it's baffling that they didn't see these issues beforehand. Who on earth would want the same Exotic gear that everyone has? Same with weapons?
At this point, I'm too tired with the game to complain about its faults, and especially since OP nailed it.
PvP and PvE has no bearing on how well you do. So right now I see a lot of people go AFK and pray upon the RNG lords to bless them even if they do squat. Did Bungie not foresee that? If so, that's unbelievable.
Building faction/Vanguard/Crucible rep is a way to earn Legendary gear, but think about this: after level 3, what's the point? See?! Again, it's like Bungie didn't think this thoroughly.
I've stopped playing Destiny for about a week now. The "events" are seriously underwhelming since they're the same story mission shit with new (lackluster) rewards. I'll repeat what others have been parroting before: Bungie only wants you to play THEIR way, even if their way is subpar.
I've been playing since launch but I've yet to tackle the Nightfall or Raid. You know why? Because I can't find that many people playing at the same time as I have who wants to do 'em. I've already tried GAF, but nope. SEE?! I've poured a ton of hours into the game but no Raid for me since Bungie doesn't want matchmaking in that mode, Nightfall or even others for some stupid reason.
Loot cave was the most social part of Destiny, but Bungie took it out since it's not how THEY want people to play. Well, people wouldn't even be camping a damn cave if they made RNG and loot a fun way to earn.
At the end of the day, Destiny has core mechanics, but a broken loot system that suggests Bungie bit off more than it can chew with Destiny. Don't get me wrong, I still like Destiny and I still might come back provided the DLC brings something good, but it's nowhere near Halo. I agree with the others that maybe the key personnel that left affected Bungie way more than we know. Either that or they got lucky with Halo.