This!
I got a bunch of our community to try out many of the different chat systems out there. Zulip was an interesting one as there were two points that really changed their perception of it as a platform:
1. When they were told there was a "Night Mode" - aesthetics are important! (something Slack arguably got right, IMHO beyond that it's just fancy IRC).
2. After around 5-10 minutes of playing around the penny drops as to why the stream and topic "zooming" is implemented in the way is it. Usually a "Holy Cow" moment.
Once you "get" it, going back to anything else feels like going back in time.
Yes Slack has threads, but they aren't implemented in a way that's conducive to ad-hoc interaction over longer periods of time.