If Google had stuck with Wave, and applied proper product management to it to refine the design feature set, it would be Slack+Notion today and I'd enthusiastically be using it.
Google Chat in the early years worked with Jabber clients. Maybe with Wave they changed the protocol? That killed any interest in Google's chat technologies for me.
Still haven't ever used Slack. My office uses Teams now. It works but it's pretty unpleasant. Gets the basic task done I guess.