That’s a hyper-simplified False Choice Falacy, not a rational argument.
If your process for righting old injustices requires committing even more widespread newer ones, it’s not Just and it needs rethinking.
I think that if you can have some standard of proof for the crimes and can trace both the victims and the proceeds of the crime to the present day it’s just to compensate the descendants of said victims by confiscating the proceedings of the crime (for example, what’s being done with paintings stollen by the Nazis).
However being born within the present day geographical borders of a nation whose elites were (or even are) criminals is not itself a crime nor does it make one a benificiary of the proceeding of the crime (possible the reverse, as criminal elites are way more prone to also pillage their own country than they are to share with their countrymen the proceedings of their pillaging abroad) and being born within the present day geographical borders of a nation containing an area where in the past those crimes were committed does not make one a victim of those crimes.
(To cast blame or claims of victimhood on people merelly based on the place they were born in is a pretty straighforward form Descrimination)
The situation with the paintings is extremelly easy to solve in a fair way because the paintings themself are proof plus it’s mostly (sadly, not always) reasonably easy to now, 2 generations later, find the handful of descendants of the victims, but it’s way harder to trace long ago human exploitation (including the evils of slavery) to present day benificiaries of said crimes because it long ago became money and money is fungible and got spread out, dilluted by money from legal sources or even totally spent by an earlier generation.
I’m not saying an effort shouldn’t be made, I’m saying that it should be made with the proper effort, not some bullshit group blame and group compensation that leaves the ill gotten gains of the Portuguese Old Money untouches (by taking it mostly from everybody else) and further enriches well connected elites in some other nations rather than the people who need that money the most.