To the last poster: sorry I'm late, I hope you had a wonderful 2022 trip
And to @KBrylczyk:
Make sure to visit the Anthropology Museum, it's huge and it's amazing. I'm asuming you're staying somewhere close to Paseo de la Reforma, the museum is right on that same avenue. A visit to Chapultepec Castle is also great and very close too. I wouldn't reccomend the Frida Kahlo Museum, it's not that great and too expensive for what it is.
A somewhat hidden gem is the Templo Mayor ruins next to the Cathedral, there is a pedestrian bridge that crosses over them and also a small museum.
I'd reccomend you book the Turibus sightseeing tour, it's a hop-on hop-off double decker bus with various routes along the touristy parts of CDMX, with great photo opportunities and multi-lingual guides.
Places to eat/drink: Tacos El Rincón de la Lechuza in the southern part of the city, Azul Histórico (very good gourmet mexican food), Templo Mezcalería (try the Oaxacan tlayudas, guacamole con chapulines and mezcal cocktails).
AVOID: Tacos Orinoco and Restaurante Pujol. Very popular among visitors but really awful food.