Spammers don't care if it's fruitful - they just run software that finds every forum and spams it. That's why you can block so many by asking "is an elephant big or small?" on the sign-up form.

Old forums still exist and work just fine without any CEOs pontificating about "community".

I'm on plenty of niche interest boards built on PHPbb, Xenforo and Discourse. Chronologically ordered discussions, RSS support, no algorithmic "For You" bullshit.

Build it and they will come.