I find per-incident discussion spaces far more productive. I.e. if you want to talk to me and some other people about something, create a space (channel in Slack jargon). That way everything about that conversation has it's own isolated history. I can control my notification settings for that conversation sanely. If I need to find a message from that conversation, I can limit my search to that channel.

My manager heavily pushes us to use Threads for that purpose in Slack, but Slack's handling of Threads is just miserable. It's one my biggest peeves about Slack. If I get mentioned in a Thread, Slack will ping me for every new message (and I've been pinged on threads that went on for several hundred messages). If I need to find a message in a Thread, scrolling back is useless, I have to use search and just pray I have the right keywords.

I think I'm just burned out on Slack; they need to find a method of communicating and invest into it instead of their current "you communicate however you want and we'll halfway support it" method.