The real problem with decriminalization of drugs is the lack of support for those who are using drugs.
Drugs become an avoidance coping mechanism for many of the users. If their lives sucks, they’ll keep doing drugs. Some of them keep using drugs because it’s also very addictive.
If you really wanna implement a decriminalization of drugs, you must also implement health care and social security care, probably for free. It’s necessary that people have access to psychologists, social services, medics and job opportunities.
As the psychologist Bruce Alexander said: The opposite of addiction is not sobriety, it’s connection.