You can easily mute channels you're not interested in or are too high traffic tho? I usually mute most channels except for a handful I use for my current project/team. And when I need to concentrate I put slack itself in "do not disturb" mode (usually a couple times per day but not for very long each).

Also make heavy use of threads and starting new channels to keep from having a handful of "general" channels that are both high traffic and containing a lot of important info.