But what we find is that it's not just that this content spreads; it also shapes the network structures that are formed. So there's feedback between the effective emotional action of choosing to retweet something and the network structure that emerges. And then in turn, you have a network structure that feeds back what content you see, resulting in a toxic network. The definition of an online social network is that you have this kind of posting, reposting, and following dynamics. It's quite fundamental to it. That alone seems to be enough to drive these negative outcomes.

Trying to grasp it in my own words;

Because social networks are about interactions and networks (follows, communities, topics, instances), they inherently human nature establish toxic networks.

Even when not showing content through engagement-based hot or active metrics, interactions will push towards networking effects of central players/influencers and filter and trigger bubbles.

If there were no voting, no followable accounts or communities, it would not be a social network anymore (by their definition).