Its more like classic IRC than everything else. I think it's even more ephemeral than Slack. Most servers have two channel types: slow announcement channels that only owners post to, and fast conversation channels for fans, content creators, etc.

Any important announcement like release notes will be in announcements. Announcement channels have no discussion directly inside them.

The conversation channels are like message rooms of old. Usually the conversation channels have important or common questions answered in pinned posts. Unless you want to talk now, they are kind of useless. Also you need to spend some time in them before you know people and how best to use them. You can jump in and ask a question, you might get an answer.

It's a power use interface, and takes some time to learn. Once you learn it, you will miss features in other apps.