Complete control over attention maybe, but not complete control over what you see. Google targets your results like Twitter and Facebook target your feed. Reddit and HN don't do this.
I don't think a continuum along a single axis can reveal what's truly pathological about social media. If you break it up into multiple axes, I think problematic tech will cluster into quadrants where algorithms are targeting you personally in various ways.
At one end, you have the default Reddit front page. You get a torrent of posts completely unrelated to your specific interests or people you care about. It's as close to "the front page of the Internet" as you can get. Like staring into the collective psyche of the web.
At the other end, you have Google search. You only see pages you specifically request for by an explicit search query at that point in time. If you don't search, nothing is given to you. You have almost complete control over your attention.
Social media sites/apps are generally points between those. Critically, most give you more flexibility in how you use them than users get credit for. If you use Reddit by just browsing the front page and not even logging in, yes, it's the worst of all possible worlds. But if you create an account, unsubscribe from all the default subreddits, and only follow subreddits that are interesting to you and well moderated, then you have a lot more control. My Reddit experience is uniformly positive and enriching.
Twitter can also be a nourishing experience, but you have to be careful about who you follow, and turn off retweets for most of the people you follow.
Facebook is harder but if you disable all posts from sites that users often reshare, that removes a ton of clutter. Unfollowing people also helps.