I certainly know many people in countries from which these things were taken who think they are safer somewhere stable - I have heard exactly the comment that returning things will probably mean then end up stolen by politicians from Sri Lankans with regard to the things the Netherlands returned to Sri Lanka.
Also, consider what would have happened if the things from what is now Iraq had been there at the mercy of the likes of ISIS.
In many cases the people know occupying a territory have a different culture and history to the ancient people who made something. They may even have been the conquerors who destroyed the culture that made artifacts.
You cannot put that as a reason to keep the artifacts in the UK, of all places.
And of course there's a lot to say about it, even taking the absolute most charitable view, that's 90 years of mild effort after 3 centuries of slave trade. Considering what the UK keeps doing at that time and for the century after, I also wouldn't take the a naively charitable read of it in the first place.
The idea of reparations has come up. Should the US be paying or the African countries who profited and kept it going for another 100 years.
Reparations are a different topic and wouldn't necessarily solve the problems of slavery/colonization.
The British had the comparative advantage in shipping
PS: my question would be how many other countries you think were ahead of the UK in terms of trade slave when it was all the rage for European countries ?
I'm not sure if I understand what you're saying, but do you mean that Sri Lanka politicians stole the golden cannon or something else returned from Netherlands? Do you have a citation for that?
I’m not being facetious here, but isn’t the USA (and other nations) basically that? So much of the wealth was accrued through the “low” labor costs of early industry.