If a former slave was still alive, he/she would be owed an apology. But since that is not the case, no apology is necessary.
By apologizing to people who have not been harmed by slavery, we instill the myth that they have been harmed by slavery.
No black person alive today has been directly impacted by slavery.
It's a total non-issue at this point, and the apology only serves to foster illusions that the current populous has been a victim of something long dead and gone.