Slack depends heavily on the vulture that you build around it. I've been in companies where it was either everything in the specific channel (Discord like)/dm only, and in others, where threads have worked wonders. What caused this?

Different people at the wheel making decisions on how we will all use it, and encouraging the structure.

agreed, slack channels can definitely have the "lived-in space" feel to them (which is feel is the key point to the GP's comment)