Mexico City is a gorgeous, massive city that likely puts in the top three population wise worldwide. It's also home to over a hundred museums, hosts infinite parties and celebrations year-round. Mexico City has an evolving gastronomy scene that can put it among the great cuisines globally, and it's quite cheap. Between a remarkably efficient public transportation system, cheap Ubers, and very walkable neighborhoods, Mexico City is not nearly as daunting to get around in as many people think given what can only be called urban sprawl.
When was the last time you took public transportation to stroll among pre-Colombian ruins and climb pyramids? It's an easy trip whether you speak Spanish or not. And going to these awe-inspiring remnants of a civilization that date to 1000 BCE is not something that you need to do with an organized tour. It's remarkably simple to stroll at your own pace and go where you wish.