I agree with this. We use Slack at work, where we have a small team, and most of us are reading most messages in realtime. It works*
Contrast that to my experience with a group of volunteers who might log in a couple of days a week, communication is a lot more async, and you might not care about all the topics of discussion. I have found Zulip makes it easier to come back and catch up on just the bits you care about.
*I still think Slack encourages a "continuous partial attention" way of engaging with chat that I don't like. But, we do make it work.
Contrast that to my experience with a group of volunteers who might log in a couple of days a week, communication is a lot more async, and you might not care about all the topics of discussion. I have found Zulip makes it easier to come back and catch up on just the bits you care about.
*I still think Slack encourages a "continuous partial attention" way of engaging with chat that I don't like. But, we do make it work.