But outside that, a platform should not be making policies. Policy is the domain of the society's government,
No, can't work.
Well, I mean IDEALLY yes.
But a platform is a business - therefore in any legal system incurs liabilities due to actions of its customers - extremely difficult to shield the operator from those liabilities.
Therefore, any platform with identifiable ownership will have the necessity of protecting itself and in order to do that will restrict user activities in some manner.
Your statement is idealistic and unrealizable.
I used to (20+ years ago) consider it a personal affront when a sysop would censor one of my posts because I called out some contract broker. I had no idea about lawfare. Then later when I ran a board I got an occasional threat email from some business that objected to a comment like "scam" in connection with their business. I could have stood up to it but forums make you no money and I don't have any reason to back up someone's forgotten post, so...
Believing that a platform should give users unrestricted privileges is kind of like believing that "cloud" means more than someone else's computer. Somehow, somewhere, the buck stops.