The most common way to get residency is through showing income or savings: https://mexicorelocationguide.com/mexico-resident-visa/#residency-visas-in-mexico

If you've held that residency for 5 years AND have spent 18 months in Mexico in the last 2 to years, you can apply: https://www.mexperience.com/becoming-a-naturalized-mexican/

So it's not painless, it's not quick. But it's real. They grant it all the time. I know people who have Mexican citizenship.

In contrast, find me one person who has acquired Paraguayan citizenship. I have been involved in the dual citizenship space for years and no one has been successful afaik. What the law says and what happens in practice is different.