Well you shut down the idea yourself, would be completely non-viable due to jurisdiction issues, unless you'd want to follow the US position and even then you'd run into issues.

The biggest problem I'd say isn't necessarily the websites themselves but stuff like the app store and google play store, and things like infrastructure providers. Having your social media be removed from the apple store/google play store is basically killing them in the mass market, and we all know how incredibly selective they are especially when it comes to forbidding platforms that may contain porn(like tumblr for example and initially gab) while also but still allow twitter that is completely inundated with it. And that's before mentioning the downright mental idea that payment processors can just decide to not work with you anymore.

The social media itself I feel is the least of the things that would benefit from being treated closer to a public "utility" for the lack of a better word.

We're way past the point where people can just build their own stuff and be independent when targeting a significant audience(and sometimes even a smaller niche one), you need the support of payment providers, you need the support of app stores, you need the support of ddos mitigation companies/cdn's (especially in a post IOT world where your toaster is part of a botnet), and the list goes on.