Floored you’ve got a different opinion from me and the stuff you’ve said hasn’t changed mine so I think we should agree to disagree.
Personally, I see first names as much more flexible and mutable things. It’s very common for parents to choose first names from around the world for their child. Surnames are different because they, by their nature, in the vast majority of cases, reflect family heritage, culture, nationality, and are passed down through generations. You say not everyone called Quinn is Irish, but they will have had an Irish ancestor. It’s irrefutably an Irish name.
The surname as first name trend obviously conflates these two things. Personally I think it’s pretty insensitive, bordering on cultural appropriation, to choose a surname that has a strong connection with a culture that isn’t your own, for your child.
And it’s striking that, in this country anyway, it is mainly Irish names where this happens. I think most white British people would probably hesitate before calling their child say, Bashir, but why not Quinn?