I think you’re completely missing the point. Slack is a wonderful tool, yes, however it has awful, awful features related to being away. I can’t even set an away message. It is incredibly difficult to communicate to others on your teams that you are not currently available for slack chat but will reply later. This is a very basic feature and would go quite a ways to alleviate the issue.
"Placing blame on a [software] tool for your own failure or weakness is not the real issue here.”
However, it’s pretty fair to point out a flaw in a system. Your statement blatantly dismisses wide swaths of design knowledge. One of the major tenets of UX design is accounting for human weakness and mitigating it.
Slack does a poor job of allowing you to step away from Slack. Let me set an auto response. Let me indicate when I’ll be back. Let me set a focus mode and read messages later.