Most of all, it’s eternally baffling to me that so much of the Prequels are framed around MYSTERY plots.
This is a fatal flaw for almost all prequel writing. It can’t be a normal what-happens-next story because the audience already knows the outcome. Yet by default it can’t be self-contained, either, since it has a pre-existing mythology it has to work with, even if it’s chronologically earlier.
It takes an extremely good writer to be able to craft a story that still generates interest even though the ending is known. Lucas isn’t that good a writer–but most people in the world wouldn’t be, either.
I can’t think of a single prequel that changed the original work in a positively-received way. There’s tons of prequels, but they regularly get derided for changing something people believed about the story. For example, Captain Marvel made a few changes to how people believed Nick Fury made the Avengers. These were not popular additions to the story, despite being fairly low-key to the overall mythology.