There seems to be a lot of things that could be added. The types of thing that most studios already know Bungie especially.
Yes it does seem lack luster. All PvE modes modes all play about the same so gets very monotonous for game play. Then Bungie excluded about 80% of its player base from end game content (The Raid) so the whole purpose of continuing after the story seems pointless. I have to assume the majority of players, since they don't have end game content to shoot for, will stop playing Destiny after the story and maybe remove it from consideration for future gameplay. I certainly wouldn't consider buying expansion modules at this point. Will have to see how this one plays out. Very curious to read the comments around here by November.