Legalizing the drugs would rob the cartels of a vast chunk of their income and that in turn would allow the Mexican government to finally do something about them that will not be a country-sized game of whack-a-mole.
When this law was approved (2001) Portugal (Casal Ventoso) was the major Europe's entrypoint for heroin and everybody knew someone who was addicted, and it was impossible to walk in any city's park and not see an used syringe on the ground.
I think what's happening in the US with the opioid crisis is a bit different that requires a different solution. Regulation vs Decriminalization.
It's not "my body, my choice" with prescription drugs, because I didn't choose. I just trusted my doctor. Which I should be able to do, not have to second-guess whether they're actually working on behalf of a pharmaceutical company that explicitly values profits over human lives.
We already have an Opioid crises in the US..and this is with legal drugs. Lawmakers are already starting to blame the legal drug dealers and creators for getting people addicted.
If drugs are legalized, a person shouldn't be able to sue the dealer or creator. In the US, it seems like the attitude is "my body, my choice". Until that choice has negative consequences and then the person with the biggest wallet is sued for damages.
I don't really see happening in Portugal.