I think you're right. Basically no user content platform that isn't (heavily) privately subsidised could survive without sec 230. Facebook would either need to charge hundreds of dollars a month per user or close accounts.

I think one of the things that limits our society is that we need complex laws (sec 230 is very misunderstood, the same is true of financial regulation though) AND laws have to be simple enough that voters cannot be misled over what they do. That's a very tight constraint, sort of like building the Apollo project but only 10 year olds are allowed to work on it...