Moving here instead of the general anime thread, I realized that the biggest fault with part 5 is how static it is. You have interesting shit in the beginning, only to be "get to the church and beat the assassins on the way" and then "get to rome and beat the other assassins on the way". Even part 3, which can be argued to be "get to Dio" for the entirety at least had a lot of varied locales, the only interesting location in part 5 I can remember is the fight on the train.
Also a plot point in part 5 that never comes out is that Diavolo's daughter importance was that her stand was theorized to contain hint on Diavolo's stand only for it being completely unrelated when it comes out.