The real problem here is people, not the platforms or the products. How do I know this? Because the problems have existed far longer than any of the platforms.

Maybe people here are too young to remember how toxic, argumentative, irrational and judgmental everything else was that came previously: forums, mailing lists, Usenet, you name it.

Sure products can influence user behaviour but they can't totally change it. And if none of them (as you assert) "improve accuracy, increase thoughtfulness, paint nuance" ask yourself why: is it because all the platform providers are wrong? Or simply that's what users want?

Personally I've never liked Twitter. Of all the platforms I find it dominated by people who like the sounds of their own voices. I've described it as a "write only" platform. Even calling it "social media" seems like a stretch as there are no relationships, just people you follow and a news feed.