Science Fantasy is the way to go -- this thematically fits in Magic Kingdom, which has a longstanding focus on whimsy and imagination. Frontierland features talking bears (and soon "a race car from the big city," lol), Adventureland features talking birds, Fantasyland is focused on fantasy, and Tomorrowland fits in well with a focus on an imagined future that could never realistically happen.
Opening Epcot while Tomorrowland was still theoretically focused on the realistic future was a rare miss on the part of 1970s WDI, IMO. As it stood, they effectively had two separate areas of WDW where realistic future attractions would fit -- and I think the way in which Tomorrowland has floundered ever since can be directly traced to stretching the concept farther than it could be developed.
Eisner's plan to redevelop Tomorrowland into a land focused on a whimsical fantasy future was an act of genius on the part of 90s WDI, even if the resulting product had many flaws.
This is why I'm upset Cosmic Rewind went to Epcot and Tron went to Magic Kingdom. That seems to me to be a particularly bizarre mix-up. Cosmic Rewind fits in perfectly between Space Mountain, Laugh Floor, and Buzz Lightyear, with its focus on aliens, fantasy characters, and space flight. And Tron was the solitary IP originally considered for Epcot: there was a plan to open a Tron-themed arcade in CommuniCore during the 1980s that didn't pan out. Tron also has the vibe of a somewhat realistic future: VR, the "metaverse," mind-uploading into computers, AI. All of these are themes that resonate in hard science fiction and are incredibly topical for the current moment. I find Tron Lightcycle Run inspiring in a weird way that makes me think of Epcot and not Magic Kingdom, and Cosmic Rewind entertaining in a way that makes me think of Magic Kingdom and not Epcot.