We have been to Mexico City four times and are generally heavy public transit users wherever we go, but have been slowly transitioning away from public transit in Mexico City as our hotel choices has gotten further away from convenient stations and on the next to last trip, it was quite warm and the Metro was quite crowded. (I don't mind crowded, but I'm becoming less tolerant of heat as I get older and getting heat rashes and such.) Regardless, I heavily recommend the Transit app for most cities worldwide, including Mexico City. Transit isn't great for preplanning, but excellent for "I'm ready to depart now on a trip to x destination. What's the best route from where I currently am?"

For Mexico City, we now primarily use Cabify or Uber, because it is door to door, not hot, and there have been averaging $5USD per ride (We had as low as $2.28 for one and $9.05). While the Metro is very inexpensive, the $5USD/ride for 2 of us made it worth it. It might be a bit more expensive now since we haven't been back since the pandemic, but we would still likely go with primarily Cabify on the next trip.