Off the top of my head, it would have the tone of Facebook before they allowed public accounts outside of schools and right after they introduced news feed, it would be aggressively moderated, and it would cost enough money per month that people would think twice before engaging in a behavior that led to an account getting banned or using bots. There would be an initial setup fee of at least $100 along with a monthly subscription fee, and getting an account banned would result in a total loss of your payments and deletion of your profile.

* Users would explicitly agree that their profile posts are subject to moderation.

* Profiles would be private and users would be heavily discouraged from using a real name. Friending someone else would require an out of band secret key exchange. A new key would be required to add each person to a group and the entire group would be informed when a new user was added. The only people with real visibility would be the mods.

* There would be no advertising or tracking.

* The service would be located in a country that doesn't immediately bend over for Five Eyes, China, or Russia.

* There would be no org pages or corp accounts.

* Anyone holding public office, running for public office, or affiliated with a political campaign would be explicitly banned from using it at the EULA level. Group pages with more than X members would automatically be flagged for periodic review, and obvious attempts at political organizing for a campaign or movement such as BLM or the Proud Boys (chosen purely as examples of political movements) would result in a ban for all affiliated accounts.

* Egregious (as in obviously intentionally hostile rather than ignorant or inadvertent) racism, sexism, bigotry, etc would result in a ban.

* Any attempt at bullying would result in an immediate ban.

* Any attempt at bulk data collection would result in your account being suspended and flagged for review.

You get the idea. Social networks should be about sharing fun content with your real life social network. They should not be about self promotion, BS drama, politics, disinformation campaigns, advertising, influencing, branding, etc.