When filming “I Love Lucy” producers used tactics to make Ethel, Lucy’s foil, uglier on screen than she was in real life. This was done to put the focus on Lucy.
A similar tactic seems to have been used in 2020’s Fantabulous Emancipation of One Harley Quinn, by not giving any of the supporting actresses iconic costumes. Throughout the film Harley Quinn, the main character, bounces between many different outfits while her teammates where a mix of T-shirts and club outfits to fight crime. Cassandra Cain, Huntress, and Black Canary all have a history in the comics of having great costumes that would have Birds of Prey pop as a true super team, but they were not used for the movie.
Whether this was done on purpose to leave the focus on Harley is left to be seen, but what stands is the film missed an opportunity to push new characters into the greater zeitgeist by using them in mostly name only.