EPCOT and Animal Kingdom each have their own identities, but apparently both the Magic Kingdom and Hollywood Studios have the same identity now: realms that are apparently not real (i.e., fantasy settings), even though the Studios was originally supposed to be a real working studio. It seems as though they both have a bunch of disparate lands that don't really seem to blend together, that the Magic Kingdom and Hollywood Studios are actually quite similar in spite of their differences.
I'd say MK harkens back to the popular imagination games (many) American children used to play back when the park was built. I'm not sure what else to call them, but back in the 1960-1970's when children weren't playing board games, or games-with-rules (sports, jump rope), they played imagination games. In this era, children were mostly sent outside to play often with minimal supervision. They just had to stay like, in the yard or maybe in the neighborhood.
The common games were:
Wild West (Frontierland - or the wild parts of the USA),
Explorer (Adventureland - or wild parts of the world that aren't the USA, most often setting was jungle),
Space Adventure (Tomorrowland), and
Princess/Knight (Fantasyland).
Back then, Little House on the Prairie and Laura Ingalls Wilder's other books were very popular with girls, and most public school students read Twains' Tom Sawyer, Huck Finn or both. Wild West movies were also very common , like just about any John Wayne movie. So the girl's version of the game was more about pretending you were Laura. Boys' tended to go more for shootouts. Another version was to go in the woods and build two 'forts.'
Adventureland is somewhat played out in Up or Tarzan. Kids pretended to discover new places, new animals, or they just wanted to see the native habitat of all the animals they'd seen in the zoo. Like seeing elephants, lions, gorillas, crocs, or black panthers.
Princess/knight had a few different versions. For boys, swords were popular. For girls, it was often a game of dress-up.
Most of the above are long gone. The one other game I recall, that lasted a little longer was 'lava.' Lava = pretending the floor is lava. If you touch the floor, you're dead/out. Children play by trying to climb around a rec room: on tables, chairs, couches, toy boxes, crates, anything that will hold a child's weight.
OH, another popular game was seances and levitations, maybe combined with Ouija. Think Madame Leota for seances. To play Levitation, everyone gathered around the youngest child and tried to lift them using just 2 fingers (2 from each hand; 4 total). You pretended the littlest one was 'dead' and they had to stay stiff to make it work. Often the person lifted would be ticklish though and they'd squirm.
It was also...not unheard of for children to pretend they were part of Colonial America, and maybe a hero of the American Revolution. Colonial America was tough though because costumes were a bit tough to find/make.
I have no explanation for the lands of HS.....