It isn't like FF won't be in the series, It just doesn't need to be a focal point. I would love more cameos and side plots related to them, but too MUCH Final Fantasy and it will get handled poorly. KH2 proved just how bad the series can be at handling FF characters and having them in just to have them.
But X-2 is so fun, even if it isn't like a shining beacon of writing or anything. It has a great gameplay system and dressspheres was a good way to have a class system.
XIII-2...while not the greatest thing or anything anybody wanted, I think it still had some positives. It definitely improved on the gameplay system and made it a much more fluid experience, there was some interesting music by some amazing artists, Noel is 100x better than any XIII character even though they didn't develop him a lot, and it wasn't nearly as much of a narrow hallway as XIII was. That deserves something, at least. (And I HATE HATE HATE XIII so...yeah)