I’m sorry to hear that about your cousin.
Fortunately, not everyone is “programmed” the same, and the overwhelming majority of those who indulge in Marijuana, legally nowadays, do not experience any significant detrimental effects. Not everyone reacts the same, of course.
My point is simple. I believe you are misguided applying your cousins issues to the population in general. I take that from empirical evidence witnessed personally over 4 decades. Around %50 of adult Americans admit trying it. I suspect that number should be significantly higher.
The main reason Marijuana has been moving towards legality everywhere in this country is due to the fact that governments realized it was being consumed on a massive scale they could not stop, people were not flipping out “Reefer Madness” style, and they were missing out on an enormous amount of potential taxes.
From what I’ve observed in my life, Alcohol is far more destructive to individuals than Marijuana.
For a far larger set of the population, limited marijuana use has risks but is relatively harmless. And, for many, marijuana has bona fide benefits for the relief of pain and anxiety.
Contrary to the expectations of say, five years ago, the absurdly well-funded movement for marijuana legalization seems to have stalled. A relative handful of states have more or less full legalization, while in others, state sanctioned and regulated medical dispensaries seem to mark the limit of legalization.