The number one piece of advice they give aspiring themed entertainment professionals is that 1. You can't aim specifically for Imagineering and 2. Pick a specific discipline to focus on.
on the creative side some of the common disciplines would be Illustration, Architecture, Set Design, Writing, Entertainment Design, Theatre, Film, Industrial Design, Lighting Design, and Interior Design.
on the technical side you'd have film and stage technology, AV, computer engineering and programming, robotics, electrical engineering, and mechanical engineering
there's also the sort of production side of things - so like being a scenic painter or the producing side of things: so like business and project management which can come from a specific degree or any of the above backgrounds.