The parent comment mentioned traveling in rural Mexico, which presumably does not refer to Mexico City.
I agree that homicide rates have changed over the years. I would be surprised if it was ever wise for a young woman to go hitchhiking solo in rural Mexico though. From the story it seems rural Mexicans agree with me.
In Caracas the locals also constantly emphasized the dangers. Random airport workers would tell us to not even leave the airport unless we had a driver outside specifically waiting for us. Even on Isla Margarita locals would look at us in a panic if we were out on the streets after dark "you can't be here!!" and would go out of their way to help us get home safely.
I did once wonder if I was going to get hurt when I was pulled out of the audience during a circus show in Leon for the clown's knife-throwing act. I was mostly sure it'd be safe and faked and funny, but they blindfolded me and I certainly had a few thoughts run through my head about what I was thinking being in the middle of Mexico having knives thrown at me.
It's not particularly wise for a young woman to hitchhike in the US either. I certainly wouldn't recommend someone do it right now in Mexico, and I have no doubt that people here and there all have fears about it, but fears don't necessarily mean it's extraordinarily unsafe.
Thirty years ago, when I was a kid, my siblings and I wandered around in Mexico sometimes miles from home without an adult, talking to the locals. Everyone was super friendly, we were never threatened. People would sometimes offer us food or toys like little hand carved slingshots. It seemed pretty safe, and we didn’t get hurt during the year we stayed, other than once my little brother went to pet a donkey in a field and got kicked by it. It was a different time then, so I guess my point is you might likewise want to consider how the rates of homicide have changed over the years, where the rates are higher, who’s most likely to be affected, and how it actually compares to other countries, before assuming that everyone’s in equal danger, or that anyone’s in more danger there than here...