It's 2020
Go build it
2/ Slack + Discord aren't really optimized for community. Can get tons of users on it but very difficult to manage a community over time.
In fact, destination websites in general are in steep decline
See also, forums, blogs, etc. They are still big. But no longer destinations.
So it's actually a high bar, most simplistic products aren't better than organic communities on top of social networks
And most complex products are too much trouble for end users to use regularly