I can't imagine what a healthy adult could possibly get out of that.
Joy. What one person gets joy out of another person may not get joy out of and that's fine. But when you attempt to be the Theif of joy just because you don't like where a person is getting it from (even when that hurts literally no one), to the point where you think it's okay to shame them for it (which is basically bullying), I have to wonder a lot about not just your motives but your attempt to rationalize your own behavior.
Just because you don't do something doesn't mean it's not okay for other people. Your arbitrary deductions about their choices don't entitle you to judge them or to try to penalize them just because you would have done differently.
It costs you nothing to let people enjoy the things they want to enjoy when they aren't hurting you.
I'm not even saying she's not a terrible person (she's a self righteous harpy who I do believe is doing actual harm). The books weren't great but they were okay. But like. At the same time people read for a plethora of reasons and I don't think it's fair to be like "it's not good so you shouldn't enjoy it". People are allowed to enjoy things. They don't have to be good.
There are plenty of reasons to avoid her books without crapping on people's personal tastes.