Indeed, the only mention of cardboard boxes in the context of luggage that I can find on Aeroméxico's website is talking about transporting chickens on internal flights. (For internal flights, cardboard boxes are ok; for international flights, chickens have to be in wooden boxes).
Google also finds a comment on Facebook by someone who says (my translation from Spanish):
On Aeroméxico I brought as checked luggage a box the size of a suitcase without any problem. They only asked me not to label it as food (so a Guadalupe Eggs box wouldn't do lol), sealed with sellotape, and weighing no more than about 50lbs.
It's not clear whether that was an internal flight or an international one.
I would reckon that if it's within the normal size and weight restrictions and you get it wrapped by one of those people with plastic wrap machines (which they definitely have in Benito Juárez, because I've had my backpack wrapped there in the past) then you shouldn't have any problems, but if you want a definitive answer you'll have to phone Aeroméxico's customer support.
You might want to consider, though, whether it would be preferable to transport pottery in a hard-sided suitcase. Luggage gets thrown around a bit, and I know that when my parents bought some tiles in Spain and took them back to the UK in hold luggage, well wrapped, one of them arrived cracked from side to side.