My guess is it's due to two things.

The first is persona-centric rather than topic-centric spaces. The former emphasizes individual posters and attention to them; the latter, topics.

The second is upvoting and downvoting. As I've returned to traditional forums a bit, it's been refreshing to have the content of the posts be at the forefront, rather than the popularity. Reaction emoji usually suffice to me to fill the role of upvoting and downvoting.

Anonymity helps too, although I suspect it's mostly those other two things.

What traditional forums-that-are-not-HN are you returning to ?