I don't think you can find anyone who would disagree that individual people and states benefitted. But all those people are dead.
I've never had a strong opinion on the topic in either direction but the argument of, as you put it, "this is _our_ wealth, which we created, and which we simply want returned to us." doesn't require excess wealth to have been created by slavery, it simply requires that some of the wealth didn't go to the people that did the work to produce it resulting in those people (and their descendants) not profiting from it.
Like I said in the other place I saw this, wage theft is illegal because someone isn't getting paid for work they did, its not in any way based on that theft providing economic growth compared to paying folks.
Of course slavery was a theft of wages. But the people who benefitted are long gone.
Also generational wealth is like _the_ predictive factor in future economic outcomes. This is basic stuff.
I don't know if that line of reasoning is correct; I'm just laying it out for discussion.
The hard question from a reparations perspective is suppose that business person left the bulk of their family fortune to a particular church diocese. Let's further assume that donation was made in the form of the trust fund, so it's very easy to identify the source of a particular trust fund would not have existed but for the fact that this business person was part of the slave trade. What moral obligation, if any, does the church diocese have to repairing the harms that this donor may have inflicted on a group of people more than a century ago, given that in the meantime this church diocese has been enjoying a continuing income stream that originally had its roots in the slave trade?
One could argue, "none at all", and one could also point out that there was an awful lot of good being done by the works enabled from the income stream of that trust fund. Dismantling that trust fund (if it can be legally done; there might be donor restrictions that might make this difficult/impossible) would eliminate the good being done via that trust fund. But one could argue that this is a similar argument made by the British Museum when it was refusing to return the Elgin Marbles, and that it is a bogus one. Or someone could argue that no matter what the value of that trust fund should be, it pales in comparison that the harm that has been done, and so you shouldn't even try. Others might argue that at least admitting the truth of how an organization has benefited by past injustices is the important thing, and that reparations is not so much about money, as it is about repair --- acknolwedging and making at least some effort to repair the damage to the community by past injusticies.
After all, if someone burns down your home, what gets lost is far more than the monetary damages; it's also the emotion impact of having your home being lost, and objects of sentimental value, such as photographs, jewelry once owned by your mother, etc., which can't be compensated using mere money. All of that is true. And yet, having a true and sincere "I'm sorry" by someone who is genuinely sorrowful and repentant, can mean an awful lot.
Bottom line is "reparations" is a deeply complex topic, and it is not just about writing checks. In fact, that's arguably the least important part of the whole process. It's unfortunate that this is the part that most people who are against reparations focus upon.
The dilemma you described (using stolen goods to do otherwise good deeds) boils down to whether you want to take a utilitarian or deontological moral view. Having said that, no one (in our capitalist society, at least) would accept me stealing your car to drive patients to the hospital as OK, even if my car otherwise sits completely unused. And similarly, if I crashed your car while doing my good deed, there would be no question that I owe you a replacement.
I think the more interesting question about reparation is whether there is truly a “continuity” (of the institution, state, or country on the one hand, and of a family unit on the other). If there is, then obviously the institution owes everything needed to make you whole. If there isn’t, then they owe you the same as any other citizen.
Can you explain this? What is continuity in this sense, and why is it obvious that they owe everything needed to make everyone whole?