Editing is much, much more powerful than simply proof-reading.
For what it’s worth, I agree Lucas isn’t a very good writer. He’s got a great imagination, and a great visual sense, and I think he’d make a fantastic director of photography for somebody. He directs special effects as well as anybody does. As a case in point, there’s a shot in… I think it’s Episode 3, looking down upon the entrance ramp of the Opera House as Anakin runs in. It’s a very small corner of the shot where we see the movement, but it’s pictured and lit and colored so well that we can tell what the background is, and where the intended action is, without struggling to figure out what’s going on. The eye is drawn to the right quadrant of the screen. He’s very good at that when he tries.
What he doesn’t have is the ability to say “no.” He’s forever indulging his visual fantasies and bogging down the movie with visuals that do not serve the story.
As a case in point: there’s a scene in “Attack of the Clones” where a stormtrooper is given a command by the Emperor. The stormtrooper has a wrist-holo device, and we see a hologram of the Emperor delivering the order. “Execute executive order blah blah,” and so forth.
In “Star Wars,” a similar situation was handled without special effects. The regional governors and generals of the Death Star ask, “What about the Senate? How will the Emperor maintain control?” Tarkin answers, “I’ve just received word from the Emperor that…”
No hologram. No long-distance communication with the Emperor. An objection is raised, and dismissed, in two easy lines. Nothing extraneous. He did this because there was an artificial constraint upon his imagination: what can we do, with the budget? How can we make the shot work?
Now that he can put literally anything on screen that he wishes, George just can’t say no to a flashy visual when a competent script would accomplish the same thing with less waste and fat. He gets carried away by his own visual imagination and doesn’t (or can’t) restrain himself. If Lucas had a director telling him, “No, George, all I want is that one effect. Nothing more, nothing extra,” then he’d give us something much better.