Ending slavery doesn't reset everything back to zero. Imagine if you're running a race against someone else. The person officiating the race (no clue what this kind of person is called 😅) lets your opponent start running the race and keeps you back at the start line. Then, they have a moment of clarity and say to themselves, "Wait a second… This isn't fair!" So, they stop that person where they are, apologize to you, say they promise never to do it again, and blow the whistle so that you can both start the race.
But wait! That person still ended up starting way ahead! But we already ended head starts before the race started so it's OK, right? Well, no, because the person who got the head start still got to start from their advantaged position.
But this isn't quite the same because your issue crosses generations. So, a better analogy might be a relay race. Maybe the head start is stopped just as the second person on the opposing team receives the… thing you pass in a relay race. (Why am I making an analogy to a thing I know nothing about? 😅) They didn't personally get the head start. So, it's OK to go ahead and start the race now with one relay team already on their second runner while the other is on their first, right? It wouldn't be fair to punish that person who didn't directly gain the advantage of the head start.
Well, no, because that team still got an advantage and the other team still started at a disadvantage. Reparations are less about punishing an individual and more about leveling a playing field.