It's far better concentrating that effort on something constructive like reading a book or taking part in a creative hobby. Social media is a time suck... I would go so far as describing it as a scourge on humanity.
Would you consider participating in HN forums to be social media? I think it quite literally is that.
Yes, the voting system makes it social media. It's not as manipulative as other websites, but it's for that reason I wouldn't class it as a discussion forum.