Then you take the cool factor away from them. The coolness of villians is that people love to hate them.
If you relate to the villain too much or on their side, you lose the cool factor.
If you face off or experience the peril that the villains cause, then that is the strength of a well-designed attraction based on a film's story elsewhere.
The idea EVERYWHERE is that a park guest is a hero in a theme park. Visceral feelings of adventure and peril, then the celebration finale or outcome.
If a villain's ride has a hero assisting you, or you as the hero. How is that different from an attraction that could be anywhere in the park and why does it compliment or ask for a land based Soley on villains? Limiting and homogenizing, which is a problem Disney theme parks have had.
In Star Tours since day one, you are in the shoes of someone like Luke Skywalker, innocently exploring and called to adventure. C3PO and R2D2 are there as supporting roles the same way they would be to a protagonist. You face off with the Villains.
Back to the Future, you were in the role of a Marty McFly and Biff Tannen you directly face off/stop.
Splash Mountain, you viscerally felt the same things that Brer Fox felt through the story of him tricking Brer Fox and Brer Bear and the uncertainty when they finally almost got him.
Snow White's Scary Adventures and its incarnations before that featured the villian to give it a retelling balance and thrill of the story in the type of spookhouse dark ride attraction it was.
Alien Encounter. You were the victim of sinister events from corporate greed and a creature.
Great Movie Ride. You were in the movies and had to face a situation with a gangster/bandit.
Fantasmic would not be nearly as impactful with only the villains. What you are saying is contradictory. There are experiences where we could side with the villains, which would be odd, and/or experiences where we assist or fill the roles of a hero stopping the villains, like a good theme park attraction emulating major events of a well-known story should be.
In Guardians of the Galaxy's attractions, you are with the heroes.
Dr. Doom's Fearfall is an attraction where you are volunteering to help the villain, but ultimately the entire thing is themed to sketch and him not caring for your well being and wants you in danger and afraid. He is still a villain. Something like this can work, but the entire Marvel Superhero Island being villains only, and Marvel has some of the coolest villains, would not really make a great impact. Doom Alley is a gritty villain area of the entire land with one attraction where the over the top villain gets to remain so.
Disney has some of the greatest villains of all time. Gaston's works in a similar sense of the balance Dr. Doom's Fear Fall has. The villain is something that exists in that world of good that knows better and that's what makes them a great antagonist.
I am in no way saying Villains land is not happening. Nor would it be uncool to see(although MK is a little odd as it should just be an extension of Fantasyland, but Bob Iger has not given a care to the American Mythos of castle parks) It is just does not create the strongest impact of an overreaching land's premise.
It seems like a direct knee jerk reaction to Monsters Dark Universe land to have something akin to respond with.
The major difference, pointed earlier is that Disney villains are very melodramatic bad guys. Easy to boo, his and hope they fail because of what they always stand for.
Most of Universal's monsters are misunderstood or victims of circumstance. The humans are often the villains.
Dracula is typically the sole antagonist of the monster world by the end of a story.
@EPCOT-O.G. To go back to answer a question you posed earlier and oversimplified a bit. A world of Gods and Monsters is not exactly the same as direct Good vs Evil protagonist and Antagonist.