He is getting older, and it can be hard to be creative on demand, especially as one ages. I love his music, but I'd be lying if I said I felt his scores for th epast fifteen or twenty years didn't have a lot of... "saminess" going on with them. Listen to Hook, and then listen to Harry Potter. Granted, go back and listen to Empire and Raiders -- a year apart -- and he's obviously in the same creative headspace for both. But both of those have much more strongly-developed thematic elements than later stuff. One or two main hemes or motifs, and the rest tends to be meandering strings/horns. My only gripe about the earlier Star Wars stuff is The Imperial March. In Star Wars, Vader had a theme, but it wasn't a very well-formed one, and it lacked oomph. He definitely rectified that for Empire. The subtitle of the Imperial March is "Darth Vader's Theme". It plays for all of his scenes in Empire and Jedi, most notably when Anakin dies. I have a problem with that, by the way, if he was no longer "Vader" at that point. Shoulda been some flavor of sad Force Theme. But anyway. Vader's Theme was then also used for the Emperor's Arrival in Jedi, the launching of the Clone army in Episode II... Significantly Imperial but non-Vader moments.
For these new films...? I want him to stay on to oversee and advise, but bring in one or two younger composers who have studied and grokked him thoroughly. The music for the KOTOR games has felt more like Star Wars music to me than the last several films' scores.
And I'll echo my disappointment in not using the LSO. The difference is instantly noticeable to this Star Wars nerd. I've been able to tell the differences between the Star Wars, Empire, and Jedi fanfares for years, and Empire's version is far and away my favorite.
--Jonah