That's definitely true, but the time it really shines is when there's been a lot of conversation on a few different things while you've been away. In Slack, you basically have to read every message to see if there was anything of importance to you. In Zulip you just flick through the topics to see which ones are relevant and only read those.

We use zulip and most of the time the topic thing is used by accident. We also tried slack but it was too bloated. Honestly hip chat was the best platform we ever used. Maybe we will try rocket chat.