They're upset that there's a black man in a game that takes place in feudal Japan.
Tbh, I don't see why there should be a black character, but if there's a historical precedent or something then sure. For instance there were black vikings in Valhalla, but I know that there are historical reasons for that.
I don't think Ubi went "woke" but it does seem kinda disrespectful IMO.
Imagine if in Assassins Creed Origins, the main playable character was white. There would be an uproar.
For what Assassins Creed is worth (and it isn't a lot, and hasn't been for a long time), the stories are about the history of the country, as much as the people within it.
To take the perspective away from a native citizen betrays that intent. If Ubi wanted a "fish out of water" character, they should have continued to elaborate on Desmond's story.