Disney's Hollywood Studios never had a very profound thesis. Disney's Animal Kingdom is still rather focused. Focus on meaning and message is more important than rides.
If that's the case, why isn't Animal Kingdom the #1 theme park in the country? It certainly is the most heavily themed/messaged domestic theme-park. Yet, the place barely remains open bankers hours, and even then folks have a hard time filling up the day there especially if you aren't a first-time visitor.
I agree that DHS never had a true unifying theme - some think that the "real live studio" was a part of it, and somehow got sidetracked, but in truth it never was, nor did they ever really intend it to be a working studio. What happened was really transparent - Universal was coming, St. Eisner decided to stretch one proposed Epcot ride into an entire park to try and cut them off at the pass.
The joke was kind of on them, though, as they erroneously thought Universal was going to attempt to replicate the "working studio" park in Florida, so they spent a great deal of effort on pretending they were going to do the same - only for USF to actually open and largely had dropped the conceit entirely.
They did do a fantastic job of the fiction, though, as you can see since the myth perpetuates even today - folks really don't understand how things were entirely fabricated and what little filming ever happened (notably the MMC and that other Disney Channel show) were simply brought there to help publicize the park. Folks forget now that Disney Channel used to be a premium channel like HBO or SHOWTIME, and that little insert of the water tower saying "Filmed at DISNEY-MGM STUDIOS" with a voice over making sure you saw it was only to advertise it continually to children who's household incomes were likely to coincide with those who would take a Disney vacation - never because they really truly wanted to make a "working" studio.
In any case, I think the romantic idea of parks having a "unifying theme" which has been said over and over in this thread is just that - more of a romantic fan idea than anything else, as it really does not hold up with the mountains of evidence, way back to Disneyland.
The "Disneyland-style" parks don't really have a "unifying theme" - they cover everything from space to American history to fairy tales and literary adventures. Epcot is very famously two different themes that
literally were two models of different theme parks mushed together (and Future World is essentially Tomorrowland 2, until Tomorrowland 1 was retconned into being about the retro-future, see House of Tomorrow, etc). MGM - well, see above. DCA? If ever a park had identity problems...LOL.
So, stateside, the only park that truly has a unifying theme remotely near this ideal folks say should exist is AK, yet it's neck and neck for last place at WDW and only two places away from being the least attended Disney Park on the planet (after DCA and HKDL).
The answer is easy: attractions. More proof? Universal. Hate to beat the Potter horn, but neither of the lands built there really have much of a connection at all to a "unifying theme" to the parks they exist in - IOA marginally since that park has such a loose theme to begin with. Attendance numbers are up and have remained up at IOA somewhere around 60% due to the attractions/land that was built.
Folks come for attractions/rides, and while they appreciate very much when there are uniquely themed trash cans in each land, and when things in eyesight all match up, the overlaying "message and meaning" really isn't a concern. They don't look at the parks from that macro perspective. When you ask someone about a park, they will say, "Oh, the one with X ride?" most often as a reference point. Conversely, so many people rush through all the parks so quickly, that sometimes they can't remember which ride is in which park - while to us that seems ludicrous, we are odd ducks.
Disney needs to focus on putting investment dollars into quality attractions, the rally call for a "unifying theme" has never really happened stateside to begin with really, and when they have come close they end up paying too much attention to that aspect and missing on the reason folks come. Why did not more folks come to Florida when AK opened, why did it just cannibalize what was already there? Because it had a theme and message but forgot the most important things - it's the rides/experiences. PotC and Splash Mountain would be just as great rides even if they were in the middle of a bare parking lot - I really think that the focus on theme and such (especially now that it's so ubiquitous throughout life now - from restaurants and casinos to even dentist offices) is never going to be the draw that gee-biz-bang-wow attractions are, and Disney just doesn't seem to make those anymore.
I do hope that changes, sincerely. I have hope for Star Wars, but they've got about one more chance from me before I just give up on WDW doing anything but wallowing in mediocrity.