Be prepared.
First of all it is the gameplay for me. I'm a fan of turn-based strategy rather than Action RPG types and I thought it was pretty poor to see Final Fantasy selling out to todays RPG fans that love Action RPG rather than keeping to their routes. The gambit system is very lazy in my opinion. If you set up your gambits properly then you don't even need to do a thing. I set them up perfectly so that all I had to do was move the analog around the field and let the characters battle while I posted on a forum how lazy the system was. Sometimes the gambits just get messed up as well. I remember having my 2 AI characters (Balthier and Ashe) with the "attack party leaders enemy" gambit. I attacked some enemy but he ran away so I locked on to another one, instead of helping me the other 2 characters just froze while I was getting a bit of a tanning. The last area (Bahamut Fortress) was very disappointing. Normally they would take you ages getting through all the obsticles and fighting various bosses, but instead the final boss fights are only actually a few minutes away from entering.
Characters now, Vaan is pointless. He is in a way the main character as it is him you control in cities but if you were to only view the game by its cutscenes then you would never think he was. He barely speaks and when he does it is usually something completely pointless. Most of the time in a Final Fantasy game, the characters are their for a reason but him and Penelo are "Just a long for the ride" (As Vaan says). Basch was my favourite, great voice acting and more of a leading character than Vaan.
Story. Completely boring. I remember reviews saying that there where so many twists and turns in the game and when my brother and I were playing it, we were always trying to second guess what was going to happen, but nothing really big did happen. The only 3 twists I could remember were 1 - Vossler betraying you. Personally, I thought he was a great character and could have done something more with him but he betrays you near the beginning and you kill him almost immediately afterwards. 2 - Balthier use to be a Judge which in my opinion kind of ruined his layed back cocky character as the second half of the game he was boring. And finally Dr. Cid is Balthier's dad, which is only briefly mentioned by Vayne (I think). Also I felt that Gabranth could have been a great main antagonist but instead your characters only see him near the end when you have 2 easy battles with. Which also brings me to the most cliche part of the story when Basch reveals that he has an evil twin brother - And Vaan believes him.
Finally my last complaint is that the game is basically Final Fantasy Tactics, Star Wars and Final Fantasy XI with a different name. The game is set in Ivalice, Montblanc appears in the game, all recurring summons have been done away for the Final Fantasy Tactic summons. The game has an MMO feel to it obviously the way you have to loot and action-turn based and finally like Star Wars since they seems to be set in older times as you can see by some of the biggest cities, clothes, weapons etc are old fashioned, yet they seemed to be so advanced that they have Airships that shoot lasers that are border line on becoming space ships as well as big emperior ships and a massive battle at the end just resembles Star Wars as well as the sand people look alikes. Balthier and Fran are just easily like Han and Chewbacca. I know the creators are fans of Star Wars but I think they added in a bit too many Star Wars references.
That would be why.