I loved Wonder Woman, a very beautiful woman that didn't trash the fans even when the media were trying to goad her into it. The media interviews at the time were trying to get her to say it's a woman empowerment film for women, she had none of it and said it's just a film to entertain. When I saw that I was a guaranteed watch, and it was a very good film except the end got a bit messy if memory serves. Still it was very good, I even took a lady friend to watch it again, and she loved it too!
With Harley Quinn, I'm sure they knew it was going to be a bad film so THE go to tacitc is SJW issues and virtue signals, I'm sure it was a girly film made for girls by girls - the main problem being it was BAD with very inexperienced writer and director. When you have cast interviews, before the film is even in the cinema, calling men misogynists(Ewan McGregor) it will turn off a subset of people(me inc) that would have given it a chance. As has been said, given they said that and more men then women, 54%-46%, still went to watch it the main problem has to be that women don't want to watch this sort of film(comic based super heroes).
I'm sure it's not terrible, as in ghost busters 2016/Batwoman terrible, the marketing for this film was adversarial to the potential viewership - IE they attacked potential viewers even before they gave it a chance. If they are like me then I'm sure they voted with their wallet and saw something that actually wanted them to watch. Even the title was ridiculous, so much so they've now changed it so the normies can tell what it is.