Youre the one who demanded nuance but refused to acknowledge there’s nuance to what criteria people use to give out (personal) book ratings.

Unless you create a standardized criteria it’s all just based on what the reader wanted and how well the author delivered on expectations

Is nuance not a thing? Can I not rate a book that fulfillls its function perfectly as 5 even if it’s prose quality isn’t as good as a 20th century classic that fulfills its own function perfectly? Can I not rate 2 separate books a 5 out of 5 for completely different reasons?

Feel like it depends on why you’re rating one of those books 5 stars. I would rate a book I enjoyed a lot 5 stars if it scratched the itch I had, and that itch can vary. Obviously rating it 5 stars based on literary value is a no, but not everyone rates based on that.