The complaints are a bit interesting, just from the standpoint of someone who played WoW. That game at least would launch with a couple of raids, but at the same time, WoW players would exist in a giant lull between patches, where there was no new content. Sure, subs dropped, but the complaining didn't totally drown out the fact that 7-10 million people would continue to play MONTHS after content was consumed. Here, we're not even a week into the game, and the "nothing to do" complaints are coming in.
Thing is, WoW did something similar with their patches and expansions, where they'd put a release timer (not sure if Destiny's raiding isn't finished or being held back), in an artificial attempt to make the content last JUST a bit longer. It definitely shows the impatience with the FPS crowd, versus the willingness to almost do nothing for months, from an MMO standpoint. It really shows that cmdrdredd's point that impatience is part of the problem has some merit.
I know that I came from the FPS crowd to WoW, and I ducked out HARD a lot because content got stale, and I wasn't keen on spending $15/month to stand in a city and play the Auction House or chase an old raid mount from 5 years ago that I'd never use, just so I could sit in Stormwind and try to brag to no one who was interested or something.
Destiny seems to be a risky proposition, not due to the budget or ambition, but because they're going to push MMO ideals (whether they like it or not, this game has many MMO qualities) onto the impatient crowd (mostly the kids) of the FPS craze. If Destiny struggles to deliver enough PvE content to hold interest, then the game runs the risk of getting shoved aside for the next FPS MLG deal, like Halo: TMCC or CoD: AW. Luckily (I guess), Destiny isn't a sub-based game that requires cash flow from players willing to sit around and not do a whole heck of a lot, like WoW is.