I don't think it's necessarily just the algorithmic feeds that are addictive. Even in a social media that was completely straight forward 'friend to friend' networking, you'd still have FOMO, the curiousity about what that latest ding/notification says, and much more. And I think these things are inherently addictive.

BBS' are probably a good example of this for those who around during that era. They were basic dial-up services with some basic social features, and they were extremely addictive even though it was limited to nothing but a handful of people in your geographic region, and long before 'the algorithm' was even a thought.