I don't think it's fair to say its failure is down to incels. Wonder Woman, Captain Marvel, The Hustle,
Dark Phoenix, and that Rebel Wilson romcom were all successful and/or well liked.
Sometimes it really does come down to marketing. Most of the publicity for the film made it clear it was a feminist movie, and sometimes this publicity teetered over the "teehee, not for you, boys!"
Plus, a completely shallow point... These are the comics Birds of Prey:
and this is the movie version:
I'm all for averting the male gaze, but that doesn't sell movie tickets...