It’s personal preference. At a place like Epcot for instance, if you don’t want to blow your money on overpriced table service or “drinking around the world”, it’s easy to feel like you’ve run out of things to do. At California Adventure, though not necessarily a better park, it’s hard to feel that way because you can simply walk across the street to Disneyland when you get bored.
The density benefit is real. I think everything is too far apart at WDW. Once upon a time, I do believe the sprawl would have lent itself nicely to a relaxing resort vacation. But if you’re someone who enjoys rides and attractions foremost, the logistics of getting around the resort due to modern crowd levels make it very difficult to embrace WDW.