the main thing i've learned from this whole destiny thing is, a lot of people not only have never played a mmo, but have no idea what makes a mmo a mmo.
destiny, is not a traditional mmo, so people need to stop comparing it to wow,ff,gw2, etc.
destiny is closest to a lobby mmo, like vindictus, warframe, phantasy star. lobby mmos have different rules and standards than traditional mmos.they handle content differently and add content differently, so i'd advise not relying on expansions to turn the game around if you don't like it.
i think a lot of the problem is when people heard the game was gonna be similar to a mmo, they thought traditional mmo, which if you don't play mmos much or at all would be a fair assumption. bungie didn't bother to correct that assumption, because it generated a lot of hype, so it's somewhat shaky who's to blame for the misconception. gamers came up with a perception of how destiny would be, bungie fueled that perception at worst, didn't bother to correct it at best.
either way, the game being somewhat mmo like doesn't give it a pass for being bad in the areas critics and fans continue to bring up.
also, i've never played, or heard of a mmo that's launched with only 5-10 hours of content,that's pretty much unheard of.