As a society, we should consider if it is acceptable for a company to influence society via the way they moderate their content while being largely unaccountable to citizens.

I don't think 'start a new platform' is sufficient to address the above. Major social media platforms serve as an effective town square and speech at a real town square is protected by the first amendment.

Parler for example is a customer of AWS and Google. There are a very small number of apps that are banned for political reasons and are probably insufficient to get most people except the people with the strongest political ideology to use alternative platforms that are open to these apps.

Changing 230 with regard to what content is removed should be fairly simple. Currently, social media companies can remove content they deem 'objectionable'. The term 'objectionable' is specifically up to individual social media companies. The definition of 'objectionable' could be more narrowly defined to include only a subset of content. Social media companies could also mark content with various labels that individual users can decide to either view or not view. Changing 230 with regard to who gets banned is much more difficult.

BTW, I don't think Craigslist's "dating" subs were really for dating. I think it is more likely that most of the ads were for sex work. Facebook did open their competing dating site, but they also have many competitors that don't have 1% of the resources that Facebook has.