The excerpts I've read of her books read like Wattpad (fan)fiction. AKA mostly bad fanfiction. And at least that's free.

I also think Hoover tends to appeal more to people that just want something easy and accessible to read, mainly young people who don't read a ton or are just getting into reading, and many people who read more regularly are a bit scared of the general public either holding her up as the standard or something to aspire to, like the trend of publishing will move towards books with the same style or quality of writing.