I’ve observed after reading through many works of speculative fiction that a universal tendency, found in every book, is that the plot begins to lose coherence when the growth in complexity of the story exceeds the capabilities of the author. From the perspective of the logistics of writing this makes sense, after all authors are time-constrained when writing and have bounded intelligence. I.e. writing smart things doesn’t automatically make them smarter past a certain limit.
Although the average character in a story does sound smarter and more insightful than the average person in real life that is because the author typically spends some time working and reworking their writings and don’t just put words down off the cuff, as what regular people do in everyday situations. I.e. they have the luxury of time to think things over which usually ‘upgrades’ the level of sophistication in writing.
Eventually authors reach a critical threshold where the ballooning complexity of their story exceeds even a strenuous effort to write. The typical progression is as follows:
Simple, well written -> moderately complex, moderately well written -> complex, decently written -> highly complex, poorly written -> incredibly complex, author gives up.
This of course is relative to the authors innate level of sophistication with the best works of complex speculative fiction written by seemingly geniuses. Which makes sense because to a genius author what seems to the regular person as incredibly complex may only be moderately complex to the author. And when a new author of average sophistication tries to emulate the complex plot and prose of the masterworks they usually give up or ‘downgrade’ their work, see fan fiction.
In fact, the logistical constraints apply to regular fiction and well any writing really. I just don’t have enough experience reading those to say.
Therefore, there exists a critical writing threshold which reveals the limitations of the writer.
M. Y. Z. 