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.