They are a major carrier. It should be no worse than any of the standard U.S. carriers. All of our best flights have been on airlines based in other countries so Air Mexico might be quite pleasant. China Airlines makes my regular Delta flights look like a cattle truck.
Reportedly Delta owns 49% of Aeromexico. Modern fleet Aeroméxico - Wikipedia Good safety record as well: Aeromexico plane crashes
We used AeroMexico a few years ago out of NYC. Great service and served a hot meal on the trip. Would recommend.
It's worth the upcharge to reserve seats in Aeromexico's 'Boobs Cruise Class' front section of the aircraft. Instead of salty snacks, they offer complimentary alcohol-infused whipped cream, plastic glasses of an orange-colored sweet concoction and the lavatory can accommodate four adults at the same time Cue music .... "Oonce, Oonce, Oonce, Oonce"