I much prefer Zulip to Slack because it forces you to split your convos into topics, making it more like a forum than a realtime chat system. It also intentionally eschews push notifications in favor of keeping everything asynchronous (unless you're specifically @mentioned).
I haven't seen any chat system other than Zulip quite nail this yet, but I'm optimistic that others will eventually catch on. I'm not convinced that human-provided topic labels could ever be replaced by an AI deciding which things should be clustered, but maybe I'm wrong...