Earlier quoted context omitted.
I think this is largely the problem with mobile phones as well. Like you probably aren't going to go mad or get rectangular eyes or whatever, but you can just sort of sedate that sensation of boredom with scrolling reddit or facebook or whatever, which does all of bupkis for making us happy in the long term.
This is the same argument with all consuming vs producing. It's why there was a moral panic in the 1800s over Jane Austen style fiction, in the 1930s over radio, and so on. Being addicted to cannabis is not really any different to playing computer games 12 hours a day, doing endless marathons, watching sports, investing, or many similar activities.
I've heard professors say something to the effect of "students a decade or two ago used to be more productive". I don't have trouble believing that; so would I (I think) without the potency of modern entertainment. It's harder to do stuff while eating such good electric lotuses. :p