Moderation is actually your core challenge. Since you believe that it's something other than moderation, I don't think you are familiar with Masnick's moderation article. Anyone hoping to build a social site needs to read it.
If you do not have a viable plan for these issues, you will be on the hook for both unsavory and illegal material. It's not 1995 anymore and governments are no longer giving a pass to libertarian idealism. Most other countries do not have the robust tolerance of speech that has sometimes been a US trademark. And even in the US, not all everything you can post is legal (CSAM being the big obvious one).
https://www.techdirt.com/2022/11/02/hey-elon-let-me-help-you...
If you do not have a viable plan for these issues, you will be on the hook for both unsavory and illegal material. It's not 1995 anymore and governments are no longer giving a pass to libertarian idealism. Most other countries do not have the robust tolerance of speech that has sometimes been a US trademark. And even in the US, not all everything you can post is legal (CSAM being the big obvious one).