My understanding is that you would sue the person who originally posted the content. You can sue "John Doe" and subpoena the social media companies and internet service providers for information to identify the poster.
Which the removal or not of Section 230 doesn't change. No matter what the law says, no matter what culpability exists, if you can't afford a lawyer, you're not getting anything. An issue with the law in the US, but hardly relevant to the issue at hand.
But YouTube has deep pockets, so if you could sue YouTube, lawyers would work on contingency. What lawyer would take a John Doe case on contingency?
Worse, what if the defamer is able to hide their identity or from a jursdiction that doesn't care about an order from US courts? In that case, even paying for a lawyer won't help.
A) post video to YouTube for $0
b) contact lawyer to subpoena YT and then sue a jerk? $50,000