Not that what you're saying isn't true, but I disagree that it's necessary for a piece of historically situated media to make explicit commentary on present day events. It's fine for an artist to allow it to be read that way it as an implicit reading of the work. 12 Years a Slave didn't need footage of the Rodney King riots to be relevant.
It's not necessary, but it provides a good perspective on the causality of history that situates the viewer/player/consumer in a broader historical context that affects people to this day. Historical events and periods are not simply 'bubbles' that happened and then racism went away - they were events and instances that had a material and evidential effect on people and their descendants.
When Assassin's Creed touches on slavery, it does not comment on the repercussions it had for the colonial countries or the Black diaspora or the Maafa. The player is thus completely divorced from what went on, even though in many instances, this player's society has been affected by colonialism for good or bad. 12 Years A Slave stands on its own, certainly, as the book it is based on, only provides a limited autobiographical perspective on history. But that is not to say that it would be interesting to see the long-term repercussions and how white supremacy still is alive and well.
Historical media do not require to give perspective on historical causality, but they certainly benefit from it.
I don't see how you have to make your historical themes clearly relating to present topics; at some point you have to let the work speak for itself and expect people to infer the parallels themselves. Did I get that "Let That Be Your Last Battlefield" was an allegory about 1960s racism? Yep. Didn't stop it from being cringey and stupid as hell because they were so on-the-nose about it.
It's a difficult topic to tackle, especially when virtually every game is never trying to be a hardcore historical sim and the fun of a lot of these games and periods (especially something like Assassin's Creed) is the escapism to a more intriguing past, and I don't think lots of players want to be hammered with "the past wasn't so great!" all the time, as well as the pitfalls of turning social issues into a game mechanic ("watch as your crack meter fills to full!")
The Mafia guys from the OP at least seem to be aware of these pitfalls, and dealing with the realities of race relations in the time period seems rather central to the story they're trying to tell, so I hope they can pull it off.
I don't understand your argument(s). Commenting on the causality of history and contemporary racism does not preclude letting the work speak for itself. Nor does it mean that they have to be on-the-nose about it.