All you can really say is that negligence is corrosive to civilization, and maybe that drugs act as an amplifier of sorts for society's illnesses and qualities.
could also say a corroded civilization makes vulnerable people feel bad and drugs make them feel good
drugs have been making people feel good (and messing with their sense of motivation to behave responsibly) regardless of society's state
That's focusing on low class drug use. Elite drug use leaves a very different trail and has a different impact.
Right, and the elites can deal with it them selves, they have money. They are definitely not directly responsible for the "subterranean environments covered in art and strewn with drug paraphernalia".