HN and Reddit are both social media. Both sites are largely populated by lurkers.

I'm not sure there's a good example of a social network site left.

Even sites and services that can be used for social networking are designed to make that difficult. For example, on Instagram you can choose to follow and interact with only people you actually know and keep your profile private. That would be social networking IMHO because it's mostly one-to-one or at least one-to-not very many. But Instagram insists on showing suggested posts. You can turn that off, but after 30 days they turn it back on.