Zulip (https://zulip.org/), a recently open-sourced Slack alternative, has a clever solution for this. They have a light-weight threading model which ensure that discussions stay within context. That way, you can just ignore discussions about topics you're not concerned with without missing anything else. It's great.
> Sometimes, important things get discussed when you’re not around. Unfortunately, so do a lot of unimportant things.
> Zulip makes it easy to review the conversations you missed, so you can focus on that important project without having to catch up on how Jim’s guitar lessons are going.
This will have the same problem, slack, by design is a time black hole where you have to dance when the other side say you must. Email allows you to prioritize tasks in your own time.
> Sometimes, important things get discussed when you’re not around. Unfortunately, so do a lot of unimportant things.
> Zulip makes it easy to review the conversations you missed, so you can focus on that important project without having to catch up on how Jim’s guitar lessons are going.
Someone on HN described it very well:
https://news.ycombinator.com/item?id=10281065