In most ways they were far more social than modern social media, in that they were about socializing. The distinguishing characteristic that sets modern social media apart from the old school stuff is the performative aspect of it—where everyone is now encouraged to behave as a content producer optimizing for engagement—which is hardly social.
Those mediums do not have algorithms, feeds, followers, profiles, influencers, likes, or any features that many people point to as the toxic aspects of pretty much every commercial social media site of the last decade.
I’d say livejournal was the tipping point where the internet became very self-centered and your value in the platform was measured by how much engagement you were able to get.
Up until that point, in a world before blogs, social sites were mostly centered around shared interests and communities would aggressively police off topic content
> Usenet, BBSs, mailing lists etc. are social media
In a generic sense, yes. People did socialize.
But "social media" today really means: a proprietary platform controlled by a single corporation, where all the user interaction is ultimately just a ploy to keep the participation metrics up so the corporation can profile you better and sell more advertising.
Not everyone on Twitter uses their real name. Meanwhile I knew the real names of about half the top 20 most active users on a retro gaming phpbb board in the early 00s and had meet many in person and knew we everyone lived, what other hobbies they had and what they did for work or school.
Real names were absolutely used on Usenet especially in the early days, ditto for mailing lists (and still are for that matter), even though technically they are pseudonymous. In any case pseudonymity doesn't seem like it's relevant for whether something is a social medium or not – many social media are pseudonymous (or even anonymous, like the chans). HN is pseudonymous. Reddit. Tumblr. The various Fediverse services.
I wouldn't call the old stuff social networks. What made social networks a new thing was the social graph of connections becoming the information architecture of the content rather than topics. You found stuff (or it found you) by person rather than subject.
Usenet was topic based (eg reddit seems closest these days), mail lists were usually topic based, forums were organised around topics etc.
