Earlier quoted context omitted.
Unfortunately Slack is what is used at places I've worked at.
I prefer Slack over email... coming from using Outlook for 20+ years in a corporate environment, slack is light years beyond email in rich communication. I'm trying to think of 1 single thing email does better than slack in a corporate communication. Is slack perfect? Absolutely not. I don't care that I can't use any client I want or any back end administration costs or hurdles. As a user, there is no comparison.
The thing I hate the most is that people expect to only use Slack for everything, even where it doesn't make sense. So they will miss notifications for Notion, Google Doc, Calendar, Github, because they don't have proper email notifications set up. The plugins for Slack are nowhere near as good as email notifications as they just get drowned out in the noise.
And with all communication taking place in Slack, remembering what was decided on with a certain issue becomes impossible because finding anything on Slack is impossible.