I think the big leap that Disneyland made from amusement parks was to make rides less obviously rides and seem more like experiences. The Jungle Cruise boarded from a dock that was supposed to seem realistic and the rest of the experience was hidden and mysterious, the Matterhorn was a bobsled ride through a mountain instead of a rollercoaster, and the Haunted Mansion involved entering a haunted Southern mansion rather than boarding a vehicle outside a show building.
Of course, there have always been the Dumbos and other attractions that are less elaborate and more obviously rides. They're usually relatively contained, though, and not as visually prominent as coasters have been at Universal parks. For example, I think the equivalent of a Hulk or Velocicoaster at an existing Disney park would be received as a calamity even greater than the Harmonious barges. Imagine, for example, if they built a coaster through Africa or Asia at Animal Kingdom and told us to just imagine it was meant to simulate riding on an animal and how that would subtract from all the work the Imagineers had put into creating believable environments.