There has to be some moderation. A completely open platform would have scum posting child porn which is illegal. That would get them shut down.
The problem is that after Trump won the 2016 election social media decided to never let that happen again. They started using Section 230 as a sword instead of a shield.
Companies like Facebook and Twitter became popular because they were open platforms. Once they got so big they decided to tighten the screws and restrict what they didn’t like.
I supported company’s rights to moderate however they wanted to up until about 5 or 6 years ago. I was on the “If you don’t like it, start your own” bandwagon. The first amendment restricts the power of government, not of private entities.
But it became obvious around and after 2016 that nearly all of the media became proxy propaganda arms of one political party. Is that their right individually? Yes. When it becomes collective, even without explicit collusion, then it becomes a “public square” problem for free speech.