It's not just that the social media is filled with low on substance posts with excess anger and snark, but this incentivizes everyone to be more forceful - as otherwise the louder voices can dominate the discussion. So, it's not just a quality of people issue but also an emergent dynamic which encourages tribalism instead of substantive posts. The same people can make reasonable posts in other contexts
This need not be a unsolvable problem, and that one has to retreat places like HN relying on a single moderator(good, but doesn't scale).
One can also rely on timelines/feeds being based on Distributed moderation -
A user selects moderators or custom-algorithms who they find valuable. The moderation can be along different dimensions like accuracy, interest, or aligned with some political view.
There could a moderator whose style is to purely check the soundness of the reasoning without taking any position on the issue itself. This can lead to improved standards of discussion.
A key issue is how to reduce the energy required to moderate - typically a moderator evaluates the quality and rely on networks of other moderators each handling smaller domains.
Current discourse encourages users to sort into strongly polarized groups, whereas more nuanced feeds in social media can lead to coalitions which don't neatly align with the standard fault lines. Platforms like Polis actively encourage common points of agreement across different groups.