Not to set up a straw-man, but I'd imagine a similar reaction if someone wrote a post titled "How to use Facebook and not get depressed," the gut-reaction is "why use it if it's making you feel bad?"
If it had use then it wouldnt make people "crazy". It would make them happy. This inherently leads me to believe it has no use.
Personal experience, there is no golden rule to these things. Email , slack , google calendar. You eventually need to build your own relationship with these things and be adult enough to maintain that relationship (inbox at 0), seperate it from your emotions and be prepared to toss it to the side for in person conversation.
Its not slack that is making people crazy its the policies of using it at the company (or usually the lack there of) that make its benefit inconsistent. But it seems slack has not improved the situation but only exacerbated it.
I am. Not contributing to the discussion by dismissing the topic.