IMHO those who are disappointed with the game either (1) didn't play the beta and bought the hype by way of word of mouth or marketing, or (2) played the beta and bought the hype despite having hands-on experience with the game. Basically, people are too easily swayed by hype and don't have the sense to temper their expectations with a dose of reality. This appears to be an recent and continuing trend, and has already happened with three major "AAA" titles this year alone.
Titanfall was a good game created by some very talented developers but because it was marketed as the "second coming" and the "COD killer", largely by Microsoft who was relying on it to sell consoles, people set their expectations far too high for the game and when it turned out to be JUST a good game, people were disappointed.
Watch Dogs was a good game, but because of the hype surrounding the E3 a few years ago and effective marketing by Ubisoft, people set their expectations far too high and were subsequently disappointed.
Destiny is also a good game, similar to Titanfall and Watch Dogs, but because of the massive marketing budget and the overall industry hype around the game, not to mention Bungie's reputation as the creators of Halo, people set their expectations way too high, even despite the Alpha and Beta programs which were widely played and clearly communicated what the game was all about and should have set a realistic baseline for what to expect in the full game.
These three games were/are good games, above average, polished and very fun to play. No, they're not revolutionary. No, they're not perfect. Yes, they have flaws. But honestly, people need to get a grip and realize that hype needs to be tempered with a dose of reality and expectations need to be reasonable. Expecting these games (or ANY games) to be revolutionary is just begging to be disappointed. Revolutionary games aren't planned, they're unexpected phenomena that few people see coming. They're good games. Enjoy them for what they are. Don't buy the hype. Keep your expectations reasonable. Have fun and move on.