ILS26L,
Hazardous ? - NO! It would have been hazardous if the airline had overloaded the aircraft.
Speaking in more general terms - Is Mexico City a more hazardous airport than, say, a comparable airport at Sea Level ? More hazardous, Yes, but not hazardous per se.
At a high altitude airport, the aircraft will often times be operating all of the way to the performance limit, thus, the existing performance is safe, but no additional performance reserve exists.
On the other hand, at a low altitude airport, particularly in cooler temperatures, the aircraft will reach it's Structural Limit before it's Performance Limit, thus, the performance available will exceed that required - An increased safety margin.
Regards,
Old Smokey