Zulip doesn't do anything that a good email setup can't do. But it does it beautifully for those who can't go through the work to get that email setup. It also provides archives that can be handy to newcomers; I don't know how to do that with an email system.
@worldsendless I use Zulip on daily base for my business (as a kind of chat for my employees): maybe is just an email-on-steroids, I think is a great piece of software tho