I think the problem is that if you legally mandated moderation to a relatively strict standard, social media companies could never afford to meet the standard and still turn a profit. Nor will people ever agree to publicly fund the state to attempt the fair enforcement of popular consensus moderation. It'll always be "unfair" to conservatives, for example. Ho boy are the next 15 years gonna be fun!
But isn't that their problem, not ours? Chemical and other industrial companies made the same basic argument about the Clean Water and Clean Air acts. If your business model is predicated on polluting, then you have a bad business model and it's you, not the public, who need to adapt....social media companies could never afford to meet the standard and still turn a profit.
Whether or not we might be living through the latter part of a finite age of online social media is an interesting question. Surely not, is my guess, but if we knew for sure the next form it'd assume, we'd probably be busy working on it already, right? (not you and I, necessarily, the proverbial "we")