I haven't met anybody who moved to Mexico from NOB (north of the border) for the healthcare; not saying they don't exist, just I haven't found any. I know many people who visit for specialized medical treatments (mostly dental, some plastic surgery, and experimental drugs) because they are cheaper/available. The comment I hear most often from expats is they are surprised by Mexican healthcare. But therein lies a story.
Some of the surprise stems from cultural differences. Doctors down here are very friendly and easy to approach. It's common to have them on WhatsApp or request a house call. Nursing here is very different; it seems the patient's family is expected to take care of things nurses handle NOB. Hospitals expect payment before you leave, without question, which is a shock, especially to tourists.
Also, healthcare in Mexico is more variable than the mostly profit-driven model in the US or the single-payer system in Canada. Despite all the justified criticisms of both systems, you rarely expect to walk into a doctor's office in either country and find a complete quack. You can still do so in Mexico (I have, here at lakeside). Things that are prohibited or tightly regulated NOB are available here. The free government-provided healthcare is worth the price (wink, wink, say no more). Some local doctors and hospitals have pushed prices up since expats remain willing to pay; of course, the doctors are also providing English-language services, too.
My experience has been that you have to be your own advocate and researcher. The quack I initially used came highly recommended, and I still know people who swear by him/her. My visits to specialists/hospitals in Guadalajara have been excellent: good facilities and competent doctors, consistent with its reputation as Mexico's center for health care.
Like so much else in Mexico, the healthcare field is less controlled, more open, with fewer safeguards. That is both good and bad.