Nonsense.
Many of the historic aquisitions by "collectors" were as sketchy AF in the context of the times.
The Elgin marbles, for example, were removed from Greece by an English lord and an Italian painter while Greece was under Ottoman rule ..
The legality of this was questionable at best and a House of Commons Select Committee held public hearings on whether Elgin had acted within the law - many considered he had not. Given this hearing ocuurred well after the fact, the damage was done, and the booty was now in England being sold for a song it was all rather swept under the carpet.
A thief is a thief ... unless they are a Lord.
https://en.wikipedia.org/wiki/Elgin_Marbles#Acquisition
The Benin Bronzes and other related artifacts were straight up targeted theft as a by product of war - if might makes right then they were legitimate, otherwise they're on the same footing as objects stolen by armed invaders that kill half your family and set your house on fire.
https://www.nationalgeographic.co.uk/travel/2022/09/benin-br...