The whole premise of slack seems to be “let’s throw away everything we know about effective communication and try again”. That’s how we end up with threads nobody can follow, annoying bots and extensions you can’t mute, and a “knowledge store” that only works if you know who, when, and where something was said.

Every week I have to unsubscribe from the seventy channels and direct message groups I got involuntarily joined to.

If IRC could handle unreliable connections better I think it would absolutely trump Slack.