Name one "lingering effect" that is "obviously" related to slavery, and share with us if you would the evidence that makes it "obvious."
The whites-only economy stole money and wealth--stole it--from the slaves; it's as simple as that. It's totally unjust that it not be returned.
Question: Do you think the rough measure of justice (i.e., the size of reparations) ought to be the difference between what is (i.e., blacks' current situation in the U.S., with all of its "lingering effects") and what would have been if not for the original crime?
White people who are wealthier than they would have been had they not stolen the labor of black people.
Black people who are poorer than they would have been had they not had their labor stolen by white people.
Black people who are less educated than they would be had their path to education not been stolen from them by their self-styled "masters."
These are all blatantly obvious, and I'm almost embarrassed to have to recite them, but I guess we're dealing with a bit of an obstinate crowd.
In any event, it doesn't matter whether there are lingering effects (though there clearly are)--justice requires restitution for the original crime.
Return of the stolen wages, plus interest, would cover the vast majority of what's due.