Is Yasuke's story interesting? who knows, he's a blank slate. He was only in japan for 1-3 years and there are almost no records of his existence as admitted by the developers themselves, he is no more interesting than any exceptional human that existed in that period at that time, I would argue as a historical figure, specifically a figure related to Japanese history he isn't particularly interesting outside his skin colour. As a historical figure he doesnt make full use of the Japanese setting, there were no interesting cultural conflicts between African and Japanese national history, his slavers were European who themselves had interesting political ties and conflicts in the country, he barely spoke the language, there are no records of any meaningful feats or accomplishments and he left the country in short order. So again, the only potentially interesting thread here is he is an outsider who was in close proximity to people who were actually of note, this role could have been fulfilled by any fictional human from any country outside japan, many of which would have led to deeper cultural frictions than "oh my god he's got black skin". What I will admit is this is all irrelevant since he will essentially be a fictional character (and they should have made him a fictional character like every other AC protagonist to avoid this bullshit culture war spilling over into real historical revisionism, they didn't because they wanted cover for their politically motivated creative choice) the only reason people argue pointlessly about history is because the defence uses it as a red herring to distract from the real intent behind his inclusion.
The argument you are making is purposely obtuse. Sure, what is important is execution rather than conceit. I dont have any more problems with a yasuke type figure being a protagonist than I do tom cruise in the last samurai. The issue is WHY was he chosen and by WHO? These questions are important because it answers whether this is a piece of art or a political weapon, whether its made to manipulate or entertain and whether the writing is likely to be shit or not.
We both know he was chosen because he's black, and we both know the choice was made by woke culture warriors. You only need to look up the writing staff, pronouns in the twitter bio, a history of nothing but posts about representation, feminism and diversity, a cultural consultant whose only claim to fame is a book about underage gay sexual relationships in medieval japan, a franchise who had sweet baby consulting on their last mainline entry. Theres so much evidence its almost a caricature of woke ideological possession gone wrong. you want to make this about double standards and history while ignoring obvious context, I want to ask why low level, boring political slap fights are driving the most important creative choices in a piece of entertainment.