When I was on this forum years ago there seemed to be a general dislike for the character verging on hate in some posters cases. It doesn’t seem any different now and I’ve never really understood it myself as she always been one of my favourites. Also the attitude on here seems out of synch with her general popularity. To the best of my knowledge she doesn’t have an appreciation thread.
It appears to me that some people just don’t like the idea of her without the Joker, whereas to me it was one of the best things they did especially as that whole abused girlfriend/sidekick looked really yuck these days. Notice Punchline doesn’t have that kind of relationship with the Joker because they know how problematic that now looks. It’s telling they retconned parts of traditional origin story in Harleen such as her only getting through university by sleeping with her tutor.