The problem with Shrek is two-fold:
1. Ever since Avatar came out, 3D's become such a passe experience at movie theaters that 4D movies at parks have diminished in appeal and no longer feel special like they used to.
2. DreamWorks actually hurt this attraction when they released a DVD of the film all those years ago. Now that they even play it on Netflix (as the Return of Farquaad or whatever), there really doesn't seem to be a point to even see it at Universal anymore.
As much as I'd hate to see Shrek's presence leave, they really shot themselves in the foot on this one.