If it were email, those same people would abuse email. I don't think what you're saying is really a problem with Slack. Those people you're referring to are disrespectful morons.
I think the issue is that people already learned how to avoid going crazy with email. A large part of that is reading it in batches and not getting any notification when messages arrive. Some other people are bothered by this and seem to forever seek a way to worm their way back into your foreground attention.
Slack conflates mentioning someone with notifying someone. Some of my coworkers use mentions like metadata. They think they are creating a better informatics resource by mentioning people by their Slack id instead of their name. They had no intention of it actually sending an immediate notification to interrupt anybody.
They see Slack more like some kind of wiki and not like a chat system. I see Slack as a chat system and an even more worthless wiki than all the other wikis everyone creates and then abandons due to editorial debt. Unfortunately, we don't get to join different Slack systems with entrance exams to filter out the wrong sort of user...
Slack conflates mentioning someone with notifying someone. Some of my coworkers use mentions like metadata. They think they are creating a better informatics resource by mentioning people by their Slack id instead of their name. They had no intention of it actually sending an immediate notification to interrupt anybody.
They see Slack more like some kind of wiki and not like a chat system. I see Slack as a chat system and an even more worthless wiki than all the other wikis everyone creates and then abandons due to editorial debt. Unfortunately, we don't get to join different Slack systems with entrance exams to filter out the wrong sort of user...