I wonder how much of that is the nature of the park, like you said, and how much of that is the consistent lack of must-do rides for over 2 decades. You can reasonably ride Kilimanjaro, Everest, Dinosaur, Flight of Passage, and River Journey before 4pm, so after that point, if you're not invested in looking at the exhibits, why wouldn't you go back to the room for a nap and spend the night at Epcot or MK?
I agree that Nighttime DAK is an uphill battle. I feel like the park needs a solid bit of daytime expansion before people start to change their patterns, and I don't believe an Encanto dark ride and a carousel alone will do it. Hope we see more movement in this park sooner.