Slack has highly configurable notifications. Nobody sane is expecting anyone to read and react to 100+ channels in real time. One important thing to realize is

Slack has highly configurable notifications. Nobody sane is expecting anyone to read and react to 100+ channels in real time. One important thing to realize is that you are ultimately working with humans. There isn't and never will be magical tool that will shield you from this. You can either establish clear boundaries acceptable for both sides and configure notifications accordingly or change your group of humans to another, which will accept your pattern of communication. If neither is possible, then yes - it's your problem not theirs or the tool's.