> In a sense yes

By definition, yes.

> is any newsfeed with a comment-section or a hobbyist forum social media?

Some are just larger and more centralized than others.

> Can I monetise my contributions here, advertise products, sell my karma-points or create networks of like-minded individuals here?

"Show HN" basically is that. And yes you can create connections here. I don't think I need to go on.