To go from a brilliant satirist to becoming terminally online and just completely falling off the far right cliffs of insanity is incredibly sad. And unfortunately, this is plight is not uncommon. It is incredibly dangerous to make politics part of your identity and then just absolutely bathe yourself in a political media echo chamber.
It seems to me that social media belongs in the same "vice" category as drinking, drugs, and gambling: lots of people can "enjoy responsibly", some make a mess but pull back when they see it, and some completely ruin their lives by doubling down.
Most people crave social interaction, and when others engage with them it triggers that dopamine hit. As you say, we all have need for social validation. Even HN has that effect, and it's not engineered to elicit it as far as I know.
Even USENET had that pull, and people would waste hours on it, engage in flamewars, etc.
Now platforms like TikTok and Instagram might optimize for it but even if they didn't, they would have that addictive quality.
I don't think there's any way to do social media that would avoid this.