Oh geeze, LOL.
First of all, when the ride was created (during 1986, it opened in 1987 at Disneyland), there was no EU to speak of. There were no novels, everything was based on the films, with the exception of the Marvel comics which were considered non-canon even then.
Second, even today, to the vast majority of the public (and many, many fans) the films are Star Wars to them. And most of the EU is based on characters from those films in one way or another (with very few exceptions, i.e. SoE).
If you took a random frame out of the old ride and showed it to someone, a screenshot of the film, quite a bit of it would be generic. It would be very difficult to identify it as "Star Wars" at all. Spending 1/2 the ride time bouncing around a generic 80's/90's "3-D cave" (for other examples, see Body Wars, Back to the Future, etc.) really isn't very iconic of Star Wars.
The old ride was great. I loved it dearly. And I hope they have some way to put the old ride film in the new ride for special events. However, one complaint people always had was that there was very little "Star Wars" aside from the ending, and in the new ride it's Star Wars at every single moment. When at the Launch Party I asked one of the Imagineers about this and they said it was very intentional, as it was part of the mission of this ride to make it as Star wars as possible as they saw it as a fault of the previous version.