If someone is mass producing stolen data and profiting greatly on it, I agree that's not good. I also understand that producing and selling stolen data is illegal, even if Nintendo is fairly lax on enforcing it.
I think intent matters in regard to ethics, and I don't personally believe all the people selling on Etsy are doing it to get rich. For all we know, some of the people selling may have lost their job during the pandemic and may be struggling to make ends meet. Some people may just want to help other players get their favorite villagers while covering their overhead costs.
It's not an ideal situation, and I understand your stance. I don't personally think it's fair to judge all these people and call them unethical when we don't know their motives or financial situation.