But where’s the line? You could say the same about the Internet (or movies or books…) It can be used badly, but also to learn and reduce mundane tasks, unlike social media (though you actually can learn from social media, asking the AI is way more effective).

There isn't a line, just like 'dangerous speed' isn't a line. The addictive and deleterious effect of a technology is more like a continuous quantity and as that quantity increases, the probability of misuse and deleterious effects increase too.