I think it's a classic case of "meh/okay author, unbearable fandom". Some things can only get shoved so many times in your face before your indifference turns to frustration and some fans can be very aggravating without realizing it. I never read anything by Colleen Hoover because her books aren't what I enjoy, but you see her everywhere and people who love her can get quite passionate and, from what I have seen, are quick to jump to "well, if you don't like it, you obviously are boring/are an elitist/hate stuff made by and for women". So I don't think it's a problem with her content and more with the way it is publicized.

That's the problem with many divisive authors/books.