I'm going to be really selfish and champion Frida's "home-study" as worthy to be WHS. The architecture is not that special if you have been to places designed by Le Corbusier but might find a niche with the committee, yet I think the empowering large windows that let the sun into the massive studio makes me feel it is worthy alone. The other buildings I find only kinda interesting and it is mainly a museum with pictures and explanations so I was done quickly. Instead I was relaxing on the benches just across the main facade and imagine Frida's life here (well, also Diego Rivera but I kind of always have to think about Alfred Molina). Definitely something you should include on your Ciudad de México itinerary.

The entrance ticket also includes her home which doesn't have the best access via public transportation so I recommend a taxi ride.