Tough. I'd say the attraction most in need of refurb is the Indy Speedway. The cars are noisy, dirty, not fitting of the Tomorrowland theming and most importantly, very difficult to operate for little kids who seem to be the ride's target audience. How about electric vehicles? How about something easier to steer? I was at Dollywood about 2 years ago and their similar ride beat WDW's hands down, from theming, to being electric vehicles, to ease of operation for the kids.
Other than Indy, from my recent trip, I would completely overhaul (or just plain get rid of): Jungle Cruise, Country Bear Jamboree.
Needs updating: Spaceship Earth (I know, its in process), Haunted Mansion (I know), The Great Movie Ride.
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