Counterpoint: I don't message my group of friends over Slack to socialize. And I don't message my teammates and coworkers over Whatsapp groups to organize projects.
Counter-Counterpoint: My group of friends has a slack channel that we use essentially as an IRC chatroom where we organize long term events, plan evening activities, and chat about an assortment of topics. Nothing about Slack makes it less useful as a personal communication tool as opposed to business communication.
Does something about this new app make it less useful as a personal communication tool as opposed to business communication, for the use case of how you communicate with your friends?