The destiny world is rather huge when you lay it all out. And it's all explorable. The differences are in types. It is not a Dark Age of Camelot or World of Warcraft "persistent" MMO. It is an instanced MMO like Guild Wars. Persistent is never changing, the same level 1 mobs right outside your capital cities are always there. Instanced allows places to be revisited and have it appear as though time passed since you were there. Persistent allows for the population of a server to exist in 1 place. Instanced forces narrower populations in a set place. Even persistent MMOs use instanced areas, specifically their raids. Destiny allows you to send invites to anyone, or try to join anyone in a group from the roster screen as long as they're public. This is no different than WoW. And raids are most certainly coordinated with static websites, forums... And most importantly, socializing with people to join a guild. Destiny is an MMO. There's no debate to even be had.