The chief symptom is a mythically elaborate, spectacular, apocalyptic and fantastically dull confrontation between good and evil, about whose representatives there is nothing substantial left to learn.
This is suffered by films that owe their existence purely to a marketing franchise momentum that has long since outlived the original creative excitement. A t the end of the last Harry Potter film, this series began to succumb to a bad case of what the industry calls the "Matrix Revolutions".