I’ll go with the low-hanging fruit: Mein Kampf. I’ve read it, cover to cover. As a piece of propaganda, it’s good. As an example of good writing? Absolutely not (though I will admit I have only read it in translation). Oh, and the whole fascist, racist, and generally shitty worldview of the author that he infuses into the text. And the fact that the author is literally Hitler. You 5-star that book? You’re a Nazi. Period. And as a Jewish person, I don’t look too kindly on them.
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.