As a disclaimer, I know that this is controversial, but I'm against censorship. I think that it's up to the law enforcement to deal with legitimate threats, and S230 exists for this precise reason.
That being said, I can't think of any good solution if you'd like to keep that kind of stuff of your platform. I think it's basically impossible. The only solution that could deal with that amount of posts would be AI. But the problem with AI is that:
1. It's imperfect and generates false positives. There were stories about people being locked out of their Google accounts for no reason, without any possibility to appeal, because their support is also ran by AI.
2. It can get too perfect and thus extremely dangerous in wrong hands. (I think it's already in the wrong hands, but you get the point)
What's also not fine in my opinion is pulling down other services for their inability to deal with such content, when Twitter and Facebook themselves can't keep this stuff out.