[Noos]

There's no "engagement." It just ends up with banal "I agree" posts that add nothing to the article. And it doesn't add many to them, Polygon's comment sections tend to be tiny and not worth reading, for example. You get better news and engagement on reddit.

[Fellshard]

They used to be larger, and I believe that restrictive, inconsistent moderation drove people away, but that's merely a guess of one probable cause.