What happened to mailing lists and message boards?

The last dozen or so open source projects I've become interested in all seem to say the same kind of thing under "Community" or "Support" or "Get Involved" and it strikes me as odd.

It's something along the lines of "Join our Discord" (or Slack or similar).

Back in the day projects usually offered a synchronous and a non-synchronous forum for discussion. Django had a mailing list and an IRC channel.

Now - I can understand how Discord and Slack have ended up replacing IRC but somewhere along the way we've lost the asynchronous option. The one that's searchable, structured. The one you check to see if the thing you're asking has already been asked a hundred times. The one that has permanence.

Can someone explain why this has happened and if I'm alone in feeling like something has been lost?

I might be looking to start a community around a project myself soon and my instinct is to start something like a forum or mailing list and only tack on chat if there's a call for it and sufficient number of people.

Will everyone under 30 look at me like I'm mad? Do people still use these things?