The Star Wars prequels, in a brief summary, told the stories of Anakin Skywalker's descent into the dark side, the fall of the Jedi Order, and the rise of the Sith throughout the Galactic Republic, leading to the Empire in the Original Trilogy. While they were not as critically acclaimed as the original trilogy, nowadays the Star Wars prequels have become classics in their own way.
One way the prequels fell noticeably short, though, was in their lack of development. The audience is given a politically oriented trilogy instead of a traditional sci-fi-romp, but the films very rarely explain the finer details of these concepts.
10 Concept: The Motivations of the Separatists
The Separatists are introduced in the prequels as the foil to the Jedi and the Galactic Republic, but they weren't just bad for the sake of it. Count Dooku turned his back on the Jedi Order and became the head of the Separatist Council because he was an idealist who hated the corruption of the Galactic Republic's politics, for example.
However, in the prequels, these finer plot details are rarely mentioned. They're filler moments in the films. Star Wars is a franchise largely devoted to spectacles, and although the Separatists have their reasons for opposing the Republic, they are presented merely as the "big bad evil" guys.
9 Character: Darth Maul
Darth Maul immediately made an impact on audiences in his debut in Star Wars Episode I - The Phantom Menace. Maybe it's the tattoos, the double-ended lightsaber, or the horns; one thing's for certain, though, audiences wanted more of Darth Maul.
Maul barely has any speaking lines in the movie but is allied with the Separatists and is the apprentice of Darth Sidious. Hardly any of this is explained, most of it is implied. His role in the prequels could have been much larger too, perhaps as a trilogy-long villain instead of a side character in one.
8 Concept: The Complex Political Landscape
The prequel trilogy is different from the original trilogy because it takes place during the height of the Galactic Republic – along with all of its politics, interplanetary relations, and subterfuge. The prequels do not focus on these aspects like they should have, though.
The Jedi Council sits above the city of Coruscant, the Separatists are shown meeting on Geonosis, and there is dialogue that implies a complicated array of conflicts and negotiations. However, most of the movies are dedicated to flashy spectacles and loosely connected plots.
7 Character: Shmi Skywalker
The audience is introduced to Shmi Skywalker in Episode I and see her death (and Anakin's subsequent turn) in Episode II. Her role in Episode I is prominent during the Tattooine segments, but viewers never see how her life continued after her son became a Jedi.
While Anakin wasn't allowed to visit his mother after being taken away for training, Shmi's role as the mother of the future Darth Vader could have been more than a re-hashed catalyst for Anakin's anger and revenge.
6 Concept: Day-To-Day Life Of Regular People
Another way the prequels differ greatly from the original trilogy is how the narrative follows members of upper society, not regular people trying to survive. The rebels in the original trilogy are everyday people resisting the Empire, but the Jedi in the prequel trilogy are of a higher order.
While the rebels do consort with Princess Leia, the Jedi are interconnected with the higher members of royals across the Galaxy and are interconnected with the politics of the Galactic Republic too. If the Rebels could be compared to Robin Hood and his Merry Men, the Jedi are more like Medieval Knights.
5 Character: Kit Fisto (And Other Council Members)
The Jedi Council is shown throughout the prequels, including in Episode I which featured a puppet version of Yoda not seen again until The Last Jedi. The audience is not given any explanation of who these people are, though, and some of their names are only known because of merchandising.
Kit Fisto and Ki-Adi-Mundi gained notoriety online for their memeability (especially in stills from Episode II and Episode III) but these characters' deaths in Episode III might have meant more if the audience was given a reason to care about them.
4 Concept: Anakin's Training In The Dark Side
Anakin's transition to the dark side is a long one that starts when he was a child. He was raised on a troubled planet and faced countless difficulties in his upbringing as a Jedi, after which he was still unable to prevent his own mother's death. He turned to the dark side to learn more about the powers of preventing death, as explained in his infamous Episode III scene with Palpatine.
However, none of Anakin's actual training is shown on-screen. His eyes just turn yellow and suddenly he has access to these darker powers and unnatural strength. It would have been nice to see a few scenes of him working under Palpatine, even though their relationship was only just getting started.
3 Character: Qui-Gon Jinn
Qui-Gon Jinn was a justice-driven wise Jedi whose appearance in Episode I was all too brief for many. He was Obi-Wan Kinobi's master, and among the most skilled Jedi Masters to ever serve the Jedi Order.
Qui-Gon died in his battle with Darth Maul, but his inevitable death could have been delayed (along with Darth Maul's death) to improve the overall narrative arc of the first two movies of the prequels.
2 Concept: The Moral Grey-Zone Of The Clone Army
The Clone Army is an emergency force created by the Jedi in response to the discovery of a massive Droid army on the planet Geonosis. The Clones were all based on one person – Jango Fett – but have unique personalities and senses of self.
The creation of the Clone Army only intensified the anti-Jedi sentiment across the galaxy and especially bolstered the motivations of the Separatist Council. But, the prequels show the clones exclusively as the good guys with no exploration of the moral grey zone their existence inhabits.
1 Character: Death Sticks Guy
The Death Sticks Guy has only two or three lines in Episode II - Attack of the Clones but remains in the minds of every Star Wars fan. Maybe it's his haircut, it might be his antennae, the way he holds a death stick, or maybe it's his raspy voice.
Someone can only imagine how unhealthy and possibly dangerous a death stick might be. Perhaps Obi-Wan did this guy a favor by forcing him to re-think his life through Jedi mind tricks.