I've said this before, but the prequels did not lack in ambition. I think if you outlined the actual plots and removed the dialogue and some of the acting and nitty gritty stuff, it's just a monumentally epic and tragic story that did a f*** ton for world(s) building, even if the actual movies themselves often erred. Even if you think they underachieved (they did), that ambition allowed more coherent visions to expand what Lucas did across different mediums. It injected a lot into the creative potential of Star Wars.
The sequels' ambitions were paper thin and been there, done that. I don't think they did much of anything to open up the Star Wars universe at large for the better. At least the prequels came to a rousing conclusion with the best movie of the three. The sequels arguably got worse and worse and landed with a dud.