You want highly-paid people who could live anywhere they wanted in the world to move to Mexico? How many people that get paid bay area salaries but work remotely do you think live in Mexico?
No the downsides of Mexico are the insecurity, the pollution and the endemic corruption of authorities.
Not speaking english is a fake problem. You can learn spanish in 6 months if you live in the country, it's not a very hard language and Mexican are very social people.
It's obviously got some downsides, like not being an English speaking country, which is probably why it's not happening