If you want a good burger in the park, Taste Pilots Grill inside DCA does an excellent job, and Whitewater Snacks at the Grand Californian Hotel near the pool. Not quite the level of In-N-Out, but it's right there.
The burgers in Disneyland (Tommorowland Terrace) have only been "Eh, it's Okay..." for years. They just don't try to get it to you hot and fresh, and while the DLR Foods people claim to have gotten better I haven't been willing to try.
Life's too short to deliberately eat boring food - you get enough of it unintentionally.
--<< Bruce >>--