I don't see how Mexico is going to have a viable national full service carrier until CDMX has a viable airport.
AeroMexico should be positioned as an industry leader for connections between the Americas - the geographic location is perfect. But the gnarly immigration process makes transit a hassle, MEX T2 looks 20 years older than it actually is, and capacity is a perpetual issue.
Without the ability to serve connecting traffic, AeroMexico is perpetually going to lose out to other airlines' one-flight-a-day from their home countries to MEX, and without an international operation, the domestic ops won't be competitive with LCCs.
CDMX does not have to worry about airport capacity at least for the middle run as demand has dramatically been reduced by COVID-19 and it´s corresponding impact in the economy.
More than a new airport, at this stage, and I am afraid for many years to come, Mexico City needs to improuve the quality of the existing facilities at MEX.
My two cents.
I do agree with you that COVID-19 means that capacity is now less of an issue. But the pandemic hasn't changed the underlying reality that the MEX airport is unsuitable for running a connecting hub, even at lower volumes - there's no sterile transit area and immigration is a fiasco, the gate areas and lounges are poor quality, and the T2 facility in particular lacks natural light despite being constructed of a jillion miniature windows.
Someone once likened the MEX T2 architecture to that of Jardine House in Hong Kong (also known as "House of a Thousand Arseholes"), and now I can't unsee the comparison.
With Texcoco off the table, unless Mexico changes leadership again soon, AM is going to need to make major, fundamental structural changes to an only 12 year old facility if they want to be competitive - but I just don't see them having the funds to invest.
The frustrating part of this is that AM is a really charming airline when they want to be. The crew are fantastic and hospitable, and the 787-9 onboard hard product is right up there with the global top tier carriers. There are even aspects of their service that are industry leading, like the amenity kits (which are weirdly fabulous!) and the onboard bar (self-pour Cuban rum, water bottle dispenser and espresso machine - yes please!). All they need to be a force to be reckoned with is a comfortable transit experience, a sane connecting schedule bank (many connections right now are 3-12 hours+!) and a few more dollars invested in improving catering.
Here's hoping that Chapter 11 gets AM the resources they need to be a real competitor.