> authors aren't limited to the sociopolitical realities of 18th century South America, they can invent whatever systems they like, and then the question is whether their world-building skills are good enough to avoid obvious inconsistencies.

To do that authors need to very well versed in the sociopolitical realities of 18th century South America, and ancient China, and moden Europe, and... Most modern authors couldn't be bothered to do even basic research. Or can't afford to, because the pay is shit, and the deadlines are tight, and you have to produce a trilogy a year just to survive.

I've read a lot of scifi over the past few years. Most books are bad rehashes of existing ideas written in an extremely poor language (nouns and verbs with complete lack of adjectives and adverbs, poor and nonexistent metaphors, middle-school-level sentence structure etc.)

Fantasy books fare much better because they can easily borrow and steal "sociopolitical realities" and transfer them to pages wholesale.