I was not aware of the criticisms when I went to see it, but read about them afterwards as I followed up to learn more about the historical accuracy of the film. The movie does talk about the Dahomey's involvement in the slave trade - and the characters do critique it - but it certainly casts them in a more positive light than their main antagonists - the Oyo Empire and the European/South American slavers themselves.
Ultimately, it is a fictional story. While it was set in a setting that had a relationship with history, which involved an actual unit of elite woman warriors, it takes lots of dramatic license in order to tell a nuanced and powerful story about the women themselves. The cast - especially Viola Davis, Lashana Lynch, Sheila Atim, and Thuso Mbedu - were fantastic and their story was very compelling.
I understand the concerns about its inaccuracy, truly. But this is certainly not the first film/show to take dramatic license with history (see Braveheart, 300, The Crown, The Patriot, Argo, Pearl Harbor, etc). Those films didn't face the same kind of uproar, and that's because they're not documentaries. Neither was this film.
For me, The Woman King was a thrilling, heart-wrenching film that I thoroughly recommend watching. But I also would encourage anyone who watches it to follow up and read the actual history as well.