There are no castes in the Federation, and very few, very amorphous economic/cultural classes in the 20th century sense of the term. Even though the writing and the worldbuilding of Star Trek are sometimes flawed, the Trek universe stands for the kind of political, scientific, technological, and cultural aspirations generations of science fiction writers and fans have stood for. Star Trek is easy to love. I know, because I certainly do.
By contrast, Star Wars melds elements of both fantasy and science fiction into a saga of vast scope. The Star Wars universe is a magic universe with very advanced technology. Light sabers, spaceships that make the jump to hyperspace, and giant space stations able to destroy entire planets coexist with something called 'The Force.'
Many reviewers and critics questioned the soundness of George Lucas' storytelling as a result of this amalgamation of such starkly contrasting aspects of speculative fiction. Writers, Brin, for example, who after years of developing their own craft in the genre of science fiction, found they had serious philosophical reservations about the underlying theme of Star Wars as a result of its perceived break with the assumptions underlying most science fiction stories.
Let's enter the heart of the disturbance in the science fiction community--The Force. This is almost a religious concept. It denotes something that surrounds and envelopes all living things, allowing certain characters to move objects and themselves by thought alone. These characters can, to a limited extent, influence the thoughts of others. They can sense the presence of those in which The Force is strong. They can accurately envision events distant in space and time. These characters, in short, have psi powers--the kind urged upon fledgling science fiction writers in the Thirties and Forties by the great science fiction editor, John Campbell.
These characters, known as Jedi Knights, are born with their psi powers. By contrast, most of the trillions of beings living in the Star Wars universe can never hope to become a Jedi. They have no psi powers because their cells lack a threshold number of 'midi-chlorians.' Midi-chlorians are tiny organisms that carry The Force within every living creature--plant and animal. Large numbers of them within the cells of properly trained Jedi Knights permit them to tap that power at will.
The Jedi normally inherit a given number of midi-chlorians from their powerful, psi-imbued parents. Occasionally, children such as Anakin Skywalker are conceived merely through the will of the mother's midi-chlorians. As in the mythopoetic conception of Jesus, fathers are not needed in such instances. These children grow to be very powerful, and potentially very dangerous, Jedi Knights.
There, you have it. The Star Wars magic system--all neatly wrapped up and tied with a bow. For a magic system is precisely what The Force and its mediating midi-chlorians are. The name of these microorganisms should've been a dead giveaway to the magic nature of The Force. "Midi-chlorians" are a neat takeoff on "mitochondria," the real-life symbiotic mircroorganisms that supply our real-life cells with energy. Any body in our universe stoked with more than the average number of mitochondrial furnaces would suffer from fevers and eventually die.
Remember my hint? The Star Wars universe is not our universe. The nature of the psi-powered midi-chlorians demonstrates that fact convincingly. Neither our biological nor our cultural rules can apply to a universe that's run essentially by magical microorganisms.
What does all this mean in terms of science fiction worldbuilding? Let's go through Brin's list of moral lessons once again and find out:
"Elites have an inherent right to arbitrary rule; common citizens needn't be consulted. They may only choose which elite to follow."
Any magic system will by necessity create genuine elites in human or human-like cultures. Magic is inherently undemocratic. Why? Because magic is a direct source of personal power. By contrast, political and economic power grow out of some measure of cooperation from others. Magic power is much more like physical strength. Everyone may have it to varying degrees in a magic universe--but some have much more than others. If the power in question is so concentrated that the user can bend others to his will by thought alone, the user must quickly leap to elite status within any given magic society.
Does any fan of "Babylon 5" imagine for one moment that the power-hungry PsiCorps wouldn't have run rampant over human society in real life? In "Babylon 5," they were restrained only be screenwriters and the necessities of the 'story-arc' in which they played a key role. As a result, that aspect of Babylon 5's worldbuilding failed. This viewer was unable to suspend disbelief. If you, a science fiction writer, stick some extraordinarily powerful characters in your story just to move the plot along, and if said characters don't affect the rest of your society profoundly, consider this action as an example of bad worldbuilding.
By contrast, the strong worldbuilding skills evident in the construction and scripting of the Star Wars universe make it very clear that only a few Jedi Knights gone bad were enough to demolish a Galactic Republic. The magic in the Star Wars universe rendered that Republic inherently vulnerable and unstable. One glitch in the worldbuilding, however, makes the viewer wonder how the Republic ever came to be in the first place in the history of that universe.