Kind of. Imagine more like Google Groups or HN but with notifications when someone replied.

I guess if you use mailing lists for topics you can subscribe to, and cc'ing people for @mentions inviting them to reply, then yeah! Email can do it all. So why is email considered such a time sink? Because people don't filter conversations coming from the outside. But if they just set up a filter, then literally email is a Slack killer, no?