Just because the application has huge flaws from a certain developers perspective doesn't mean other people will share the same view.

I use whatsapp regulary along with my team to coordinate driver & share info/media quickly to allow the driver to do his/her job and vice versa. Having a desktop client is a god send for this as switching between computer/phone gets very tiresome.

It won't replace slack but it makes life a whole lot easier. Slack is a lot more business orientated and that definitely shows whereas WhatsApp has the convenience factor for people eg. driving and giving us real time info.