For me, the attraction of the Great Movie Ride is that it was mildly entertaining, but a long-ish and air conditioned break from being outside. As for Carousel of Progress, I personally find it more entertaining. But I think that one's level of interest in the Carousel of Progress is at least partially tied to their understanding and appreciation for the history and significance of the ride. Not only is it an interesting look at how much technology changed during Walt Disney's life, it was also one of the last major attractions that he worked on. While it could be updated, I don't know that it would be the same without the original scenes. And I am not sure there is any way to add new scenes without removing some of the old ones.