I think it's because we can see the potential the game has. However, Bungie has gone full 'Milk the first game as much as possible, sell as much DLC as we can'. Things were obviously cut from what we've seen before. A singular 'comet' expansion became 2 expansions.
You and me...and many other people in this thread are enjoying Destiny. But we're not enjoying it at it's max potential because of Bungies plan.
I'm going to go on a tangent, but look at Call of Duty. The release has plentiful content, plentiful things to unlock(Without much of a grind, since the multiplayer is the meat and just being their unlocks the things you want). They have their own form of bounties-Missions you buy into and have a limited amount of time to complete, and these things vary from headshots(Like the Queens bounty) or what not. But it's not needed to unlock the levels to unlock weapons, it makes it faster if you complete it.
And their map packs are just that, a few maps, recently it includes like 1 weapon, and everything is kept in multiplayer. Simple. Effective. Enjoyable.
Destiny....we have to grind factions, grind marks for gear...it's like everything is behind the word 'grind'. You want to upgrade a weapon fast? Grind bounties! You want better gear? Grind PvP. It's not...it's not 'Do PvP because you find it enjoyable'. In a loot game, you want better loot. It becomes, 'Grind PvP/PvE until you get loot'. My thoughts are a bit array right now, sorry for the rant.