I can't help but feel that if the movie had catered just a bit more to the comic fans that the box office results for the opening week could have at least skewed a bit higher. I understand that when looking at the audience of a movie, as a whole, the comic reading portion pales in comparison to the overall majority. However, if you want people to be hyped about a movie and make them want to go see it and convince others to want to see it you have to provide content that people want to see. For an adaptation of a visual medium that includes showcasing and including elements that will make people go, "Oh, that's cool.
Insert character name here is in this movie." Which aside from Harley Quinn they really didn't do. Even with Black Mask people were freaking out that he wouldn't wear a mask at all until the second trailer showcased that he would, which calmed down that issue.
Costumes and the overall aesthetic obviously can't do all the work, the actors need to be well cast and the script needs to be engaging and evoke whichever emotion is necessary at the time, but I do think that brand recognition and iconography play a pretty huge role in garnering at least initial interest in a film. The general audience won't care what characters or the overall aesthetic of things that are unfamiliar look like, but by making radical changes the studio immediately alienates the part of the audience that does know the source material and cherishes it. You wouldn't promote Harry Potter without his scar or Katniss Everdeen without her bow, so why promote superheroes without their signature looks and accessories?
Granted, not everything translates, but if it was possible to find a happy medium between what works on screen and still accurately represents the character then that is one less thing that people can gripe about. Some of the biggest complaints I saw about this movie from the very beginning was that Black Canary, Huntress and Cassandra were nearly unrecognizable while Harley was praised for her outfits. Dinah and Helena could have easily profited more from different costume and style choices, whereas Cassandra could have easily been named Sin and I think a lot of comic readers would have been more likely to give this movie a chance. After all, let's not forget, we are talking about a movie that is a spiritual, if not direct successor to Suicide Squad, there was no reason to pull their punches on costuming. We already established that Harley lives in a world with a guy in a bat suit and a human crocodile and a witch. I hardly doubt that a woman in a cape or a woman in fishnets would have been too hard to believe.
Sorry for the long-ish post. I am not trying to say that fixing some stylistic "issues" or "departures" would have resulted in a much better financial turnout (which we have yet to see how much it actually earns during its run), but I do think that WB and any other studio that adapts something from a source material automatically alienates a specific part of their audience and allows for skepticism if they deviate from what fans know and love. Adhering and minimally adapting things that may not work for a big movie allows for less scrutiny and simply eliminates one more thing to complain about.
Outfits could never fix any of the other problems this or any other movie may have, but if you are gambling on an R-rated, female-led action movie with a February release then I think the studio should have looked at who all was in their audience, what hurdles they may face and which ones they could have easily eliminated.