Web of trust. The biggest thing missing from most attempts to build social networks so far. A few sites did very weak versions, like Slashdot/s friend/foe/fan/freak rating system.
Let me subscribe, upvote, downvote, filter, etc specific content. Let me trust (or negative-trust) other users (think of it like “friend” or “block”, in simple terms)
Then, and this is the key… let me apply filters based on the sub/up/down/filter/etc actions of the people I trust, and the people they trust, etc, with diminishing returns as it gets farther away and based on how much people trust each other.
Finally, when I see problematic content, let me see the chain of trust that exposed me to it. If I trust you and you trust a Nazi, I may or may not spend time trying to convince you to un-trust that person, but if you fail or refuse then I can un-trust you to get Nazi(s) out of my feed.