Well, Casey Jr looks like a great addition and there's nothing wrong with splash areas which are very popular, especially in the midday sun in Florida in summer.
The problem with Casey Jr isn't Casey Jr -- it's the lack of total rides in the FLE. Casey Jr and Storytime with Belle and Pete's Silly Sideshow, etc. are all great complimentary pieces to a significant expansion. But they need to be just that, complimentary, not the focal point themselves. As others have frequently said, the FLE lacks "meat" -- there's a paucity of rides, which is the real draw of any theme park. Doubling Dumbo is great for capacity, but not particularly exciting. The only new rides are Little Mermaid and (eventually) the 7DMT. They really needed to have at least one more ride, if not two, in the entire expansion to really give it more of a draw and make it interesting. I don't even think they needed anything huge or dramatic -- just a dark ride or flat ride would have made a big difference in making it feel like there was something "big" being added to MK.