End of game spoilers ahoy
I think the thing that's causing the rift between opinions is the fact this: everyone is admitting there are flaws, and pretty similar flaws, I just couldn't get over them to enjoy the game, when the game became so easy that I, as Harry said, only used 2 real roles, because Sential wasn't necessary because no one hit hard enough, and then Syn and Sab didn't seem necessary (and both the party members kinda sucked at it) It became a leave Reletnless assault on and let the game play itself, which is just...boring. I don't necessarily mind that it was a copy/paste job from XIII in a lot of aspects but i did get annoyed that it was watered down, that the accessories were worthless and you were overall just straight up significantly weaker. When I'm annoyed with the actual battle mechanics this much, I just won't enjoy the game. The game did some things right, things were ret-conned in rather well, even tho I thought most of it was just an unecessary filler to carry on a story. Noel and Hope were pretty good characters, but this couldn't overcome the mechanics, the fact that serah was a weak main character, and with no other main characters to pick up the slack, the entire story just rang hollow for me, I had no connection and really couldn't care less about what happended.
As for Serah I honestly think she was almost a lesser Yuna. I felt Yuna knowing her faith, and you not knowing until the end was handled a lot better in the end, and a lot more emotionally. For Serah it was literally like "yuno you're gonna die if you keep changing time" and she was like "that's okay because it's for the greater good" There really wasn't a struggle or show of strength or anything. And I just won't get how you enjoyed Caius and Noel so much. Not enough time was devoted to really get the bond or feel betrayal, yuno Caius betrays him in the end, and when you get the flashback it's just there. There wasn't any big lead up to it, it was pretty much exactly what you already knew was going to happen without any real fleshing out. Now I do enjoy that Caius had twisted logic rather than rawr destory the world, but his logic was about on par with a 1st graders or a blunt rawr destroy the world anyways. Maybe if we got more fleshing out of Caius himself, actually saw him bond and get fleshed out with Yuel only to see her die and die again and see him get emotional, but we don't. And when we do see her die Caius is always so indifferent, it doesn't even pack a punch, I can't feel sympahtic for him, he just seems like an idiot who can't see that the entire human race outweighs one person, which is just retarded to think otherwise and WANT to end the world over it. I mean I love villains especially ones that dislay twisted logic well, but I honestly don't know how you thought that was a shining example that "delivered" or was developed well at all.
As for the ending itself, it wasn't that bad as much as it was an exclaimation point of my disdain for the game. After what i thought was a pretty weak story in general, instead of coming to any resolution, they smacked us with a "haha no matter what you would have done the world's gonna end anyways" which makes the whole story seem like one big filler set up for what XIII-3. I will admit I would be potentially excited for XIII-3 if they did it right and actually took advantage of XIII-2 being one big filler lead up to XIII-3, but the fact that they made a whole game as one big stepping stone, annoys me.