What is the country of origin? Please point out to me where the Aztec country is. Do you mean Mexico? Are they entitled to all the relics of the past civilizations theirs crushed? And yes, I know the idol in Indiana Jones isn't really Aztec, but the overall point stands.
With the exception of the very few cases where a country can actually trace its culture and history all the way back to when those artifacts were made, ancient culture and artifacts belong to humanity as a whole, not whatever geopolitical entity happens to control the land they're on at the time of discovery. It's not a natural resource, it's human history.
While we may debate wether the Aztecs descendants are now the Mexicans, they're clearly not the English.
The fact that it's human history is exactly why it can't be all stored in mostly one museum in one country
Sure, I'm 100% for returning every single aztec and mayan artefact to Mexico once they stop being a shit hole. Until then let them be seen and educate millions of people in their museums in Berlin, London, and Paris.
I'm all against theft. But once they reach the Mexican soil they will end up in some narco gang dealer villa and they'll just do coke off of it.
Uh yikes. Mexico has issues but they also have real institutions too. Further, who are you or I to say? Even if such issues exist, it's already a system in failure-state. Returning to the host country is the first step towards a success-state, even if internal theft happens afterwards.
Put this way: as long as the home nation has an appropriate facility, the artifact should be returned promptly.
Mexico has the federal department INAH (National Institute of Anthropology and History), which preserves and cares for ancient artifacts and historical sites from the Maya, Aztec, Izapa, Teotihuacan, and more. They operate over 100 museums and handle over 139,000 archeological sites, with 150 open to the public. I think Mexico would be able to handle any artifacts found in Mexico.