Like Los Angeles Mexico City is blessed with a near-perfect natural environment. It is almost always a pleasant temperature outside and usually sunny. And like Los Angeles the city has nearly ruined itself with growth that led to sprawl that led to traffic that led to smog. Fundamentally, however, it is tough to wreck paradise. Homes, art museums, restaurants can all be open to the air outside without even bothering with screens as there are few insects up at this high elevation. You don’t have to be a prisoner in your house against hot, cold, or mosquito-infested weather.
Besides this fundamental enabler there are the standard tourist things to love, i.e., great museums, spectacular public art and architecture, lively streets, lots of music, and cheerful people.
Going to public school in the 1970s in the U.S. we were taught to fear three things: Communism, drugs, and Mexico. If you’re still carrying a lingering fear of Mexico it shouldn’t stop you from spending at least 4 or 5 days here in Mexico City just once in your life.