The only use of the term "E-ticket" that is not hopelessly subjective is, "A ride or attraction that most people agree would have been assigned an E if the ticket system were still in place."
Among the non-movie tie-ins, Country Bears, America Sings, and BTMRR all fit. Also, insisting on a complete and absolute divorce from any kind of movie tie-in would eliminate even the Matterhorn Bobsleds, so you have to decide how much weight to give to this. Splash Mountain is an original log-flume ride with Song of the South decor, really. It's not based on the movie.
If all you want to say is that the high-water mark for Disney attractions was the late sixties, it's easy enough to just say so without all this unnecessary confusion about E-ticket definitions. I happen to agree that the decade from 1959 to 1969 represents a breathtaking crescendo of innovation and creativity that is not likely ever to be repeated. But things like that are not simply dependent on finding creative people and turning them loose. Decades like that are part of a cultural Gestalt that also includes technological advances and public mood and appetite. It's no coincidence that that is also the decade that gave us the Gemini and Apollo space programs, culminating in the first moon landing. There hasn't been anything like it since.