Final Fantasy is like a Grandmother
You have a grandmother, everybody does. She's old and probably quite pleasant to be around. A lot of her old-timeyness is what gives her charm and even though she is often slow or tedious, she is very rewarding to be around (cookies, dinners, etc.)
To me, Final Fantasy is like a Grandmother. Like every one of us, she started out as a child (FF1, FF2) and proved that she had a bright future in store for all of us. There was a time where some of her best qualities (FF3, FF5, FFT) became obvious and they would stick with her throughout her life. When she was in high-school and college, she was really hot (FF4, FF6) and plenty of suitors wanted to share a life with her. Eventually, she ran off to Vegas, got married, and partied like crazy (FF7, FF8). After a troubling time (FF9) she thought that she would have children (FF10) and then a divorce (FF11). After regaining her senses and realizing that maybe she should just try to get back to the way she used to be, she made some serious life changes (FF12).
Not many people liked this change - and so now, she is depressed, overweight, financial unstable, and feeling ugly. So she goes off and gets liposuction, buys a lot of expensive designer clothes, gets a nice new sports car, and makes a lot of material world friends. Some of us like what she's become - some of us are disgusted. No doubt, she's still got a bit of old self in there, but a lot of charms now are a lot more flash than substance. She is Final Fantasy 13.
But maybe she'll realize how important she is to all of us and she'll just go back to being her old self again - or maybe, we'll just learn to like her now.