While I think XIII-2's Crystarium is better than XIII's, can we at least all agree that the Crystarium itself is just a terrible and dumbed-down version of the Sphere Grid? That is my favorite progression system in any game, and since XIII is by the same team as X, it's hard for me not to be disappointed by any incarnation of it.
Like with any other aspect of the game, XIII-2 is a game for people who didn't like XIII. Makes sense to change the tone, too.
And still, it's not as much of a shift as X-2 was.
I mean... yes, but... that doesn't actually make sense? Why have a sequel if you're going to change it completely?
Also, it kind of assumes that it's impossible to improve upon XIII's story and keep the same tone. Not everything has to be a total 180 to still be good and appeal to new people.
And, yes, it's less of a tonal difference than X to X-2. But in a lot of ways, I feel like it's worse here.
For me, it made sense that Spira gave this great sigh of relief after centuries of terror had abated. For the first time ever, they could let their hair down a little. And even within that, they didn't have inconsistently-designed characters floating through the middle of every single cutscene. The things that people reference, like the concert in the intro, were logical extensions of a modern society - while I'm not going to say the execution was great, they felt like they grew out of the setting.
Pulse, on the other hand, is still very much in a difficult part of its existence, so the light-heartedness doesn't make as much sense to me. On top of that, it's not something that has logically grown out of the setting. They are just things they plopped in there from outside the context of the game by the director - a myserious pandimensional casino, a (hideous attempt at) a cute sidekick, etc.