> If they choose "platform", then they can take no responsibility for content posted, but also allow all content, and only remove content when it is required of them by the legal system (when the content is illegal and has been reported as such)

If you require the content to be illegal for a platform to remove it and there is a consequence for being wrong, that's a problem since the determination outside of platform competency, which encourages them not to act even against likely-illegal content.

Section 230 was adopted specifically to address this problem, that attempts to constrain socially undesirable content (even if aimed at illegal content) risked making online providers liable for all content under the model applies to traditional media which was viewed as not functioning at web scale, at least without inhibiting innovation greatly (of course, it's pure coincidence that Section 230 support is eroding when there are now huge incumbents that have an advantage from drastically making it more expensive to scale up new challengers.)