Whilst I’m in no way qualified to talk about history outside of my own interest I do have metaphorical skin in the game with regard to private collections as an African living in diaspora.
One of the most infamous examples of private collection being the Work Of The Actual Devil is El Negro De Banyoles, which I have written about before and hyperlinked here.
The TLDR: in 1830, the Verreaux brothers desecrated the grave of a San warrior who’d died aged about 27, stuffed his corpse, taken his grave goods, and kept his body as a part of a private collection until 1916, when he was given to the Darder museum and remained a key attraction until his repatriation and burial.
See, El Negro’s body shouldn’t have been on display in the first place - the rituals surrounding death and burial are a Big Fucking Deal in most African cultures, and Botswana is no exception. The refusal of the Darder Museum to acknowledge their wrongdoing in the refusal of repatriation so that a colonial wrong could be righted and the San tribesmen could finally be laid to rest peacefully is still a sore point for Motswana people descended from San like myself to this day.
By no means did they handle the situation with any tact or grace, but crucially, El Negro was “"properly”“ displayed in the Darder, unlike the Verreaux collection.
If repatriation isn’t possible — different rant for another day but suffice it to say I want the Herero skulls returned Immediately — then at the very least, artifacts of culture should be kept in an environment where they are protected and well looked after.
The objects of culture we have at home - Motswana basket work, ostrich eggshell art, jewellery - are all family heirlooms, and were bought when I was a littlun from craftspeople from my dad’s village of origin. Importantly to this, they’re a reminder of where I’m from, where one day I will be buried - they are a piece of my history.
Culture doesn’t happen in a vaccum. Before these things were artifacts in a museum or a private collection, they were someone’s culture, someone’s piece of home.
The least we can do is make sure they’re properly cared for, protected from damage and available to educate others with and learn from, and educate others on how they got to be in museums in the first place.
Museums afford proper care and maintenance, and education and discussion surrounding colonial history and the ethics of keeping cultural artefacts. There’s none of that in private collections.