There was never anything quite like Disneyland before, yet as the previous experiences of most those who built it was mostly filmmaking, not only did they incorporate much of their skills, but, by most accounts, wanted to create a general feel of being IN (various) films in a general way in most cases.
When Disneyland was built, there was no notion of being inside a film. That theme park design philosophy really only came about in the late 2000's, during the development of WWOHP and Carsland, but has become so ubiquitous that it may be difficult to imagine designing a park without that philosophy.
Even with Universal's "Ride the Movies" mantra in the 90's, it was really only the rides themselves that recreated the famous films. Even then, they took extensive liberty to modify and add items as needed to create compelling attractions; for example: the ET ride focuses extensively on his home planet which is never seen in the film, and Kongfrontation centered around the Roosevelt Island Tramway which wasn't a plot point in the referenced movie. Mickey's Toontown at Disneyland was "based on" the Toontown in
Who Framed Roger Rabbit?, but is almost entirely unrecognizable from it beyond the concept of an area where all the classic cartoon characters live.
Yes, many of the park's original designers came from a film background and they used their various skills to craft settings in ways that mimicked techniques used in film, but the theme park was always meant to be its own idea. The themed lands were broad genres that were popular and recognizable with audiences of the day, not a means to enter specific environments or even specific films. They relied on their film techniques because that's what they knew, not because they were trying to make an overly cinematic environment.
Fantasyland was the only land with any meaningful film tie-ins, and even then it featured several films with unremarkable box office performance, like Mr. Toad and Peter Pan. The reason Tinkerbell was used extensively in the television show intro is that she was viewed as an expendable character in the event that the park was a failure; it was too risky for Mickey or even a second-tier character like Dopey. The rest of the park was based on nostalgia, exploration, westerns, and future technology, all of which people understood without needing a specific Disney-branded media connection.
Audiences in 1955 simply didn't have the same attachment to media that we do today. If they missed seeing a television show live, it was gone forever. If they had a favorite movie, they'd have to wait years to see it again (if ever) for a theatrical re-release. Nobody had a desire to step into a specific location, because it was impossible for average people to really know the details of the environments: they saw them once and then only had their memories. There was no endlessly rewatching a film or TV series at home.
For example, I don't think there were really any Tomorrowland films Disney owed prior to 1955 other than the Season 1 episodes filmed & themed to "Tomorrowland."
20,000 Leagues Under the Sea came out in 1954, and its development was completely independent from the park and its marketing. Sets from the film were installed as a walk-through for the park's first few years in the building that would eventually house Star Tours. The Tomorrowland episodes of the TV series were notoriously late developments, not airing until spring 1955 because the studio creatives didn't really know how to tackle the subject; it's probably not a coincidence that the land was underdeveloped at opening and had the most extensive reworkings in the years to come.
Frontierland is really the land that Disney didn't have related branded content for prior to developing the theme park. But with their various television shows, Disney came to have some of the decade's most popular western characters with Davy Crockett and Zorro, and a variety of less-remembered ones that were still popular in their day like the Swamp Fox and Spin & Marty.
But again, that wasn't an issue because there was no expectation of the various lands representing branded content, they were meant to be their own thing. Sure, Adventureland was nominally based on the True Life Adventures nature documentaries and drew inspiration from
The African Queen, but those were just jumping-off points from which the land was developed. Nearly nothing in the park on opening day was supposed to be a literal recreation of something from a film, including Sleeping Beauty Castle itself. It was all a romanticized version of the general idea behind those settings, not a copy of the settings themselves.
It's still broken down by lands, it's just that there are more of them. There was fantasyland, adventureland, frontierland and tomorrowland and somewhere along the way they renamed the area near Frontierland as Liberty Square. Totally removed from frontierland. Now they are building two new ones that are called Piston Peak National Park and Villiansland which has nothing to do with Liberty square or frontierland. Things change. Yea, I know a concept hard to accept but it has been happening for years and I would bet my lunch that it will continue.
This is simply incorrect. Liberty Square has always been a distinct land of its own beginning with the marketing materials years before the park opened. Piston Peak is not going to be separate from Frontierland; it's going to be part of the land in the same way that Caribbean Plaza is part of Adventureland, or Storybook Circus and/or the Enchanted Forest are part of Fantasyland.