There is also the “brain rot” phenomenon that is common with science fiction writers.
Their first novel (that gets them noticed) is usually excellent, sometimes even brilliant.
That is why they got noticed by anybody (out of hundreds if not thousands of new authors).
The second and third novel is where they are perfecting their craft—and those are usually great.
Then “brain rot” begins to set in after that. Publishers are demanding the writer meet deadlines so the author rushes so the works lack the “finish” of the earlier novels. In addition, much of the early passion is gone—it is just a money making enterprise. Low information readers go for the “name” and don’t understand the “game”.
The only science fiction writer who managed to actually get better as he got older was Philip K. Dick, but his books were so weird and ahead of his time that nobody was pressuring him to publish at all.
;-)
Stephen King is a poster child for your definition of “bran rot” in an author ...
One sign of burnout is contempt for your audience. When you get too cynical, it's time to quit.