I honestly do not understand this fetish with decentralization, do you really want a social network filled with child pornography, violence and other shady stuff? Because that's what's gonna happen guaranteed. People are just animals without rules
You don't want a centralized internet and trust someone else to control it for you. You want control over your connection to a decentralized internet.
You have just described the world wide web. I may not want that stuff to exist, but I also certainly don't want the world wide web to not exist.
That said, governments are just organizations and very powerful organizations at that. Like any powerful organization, a government can become corrupt or tyrannical and start working against the populace. It is always a good idea to keep it in check so that its power cannot grow boundless.
So do we ban the internet or encryption?
Decentralization + filters which are either trained by machine learning or appointed by the community that the forum serves (rather than the stockholders that the platform enriches) is what needs to replace Facebook, Parler, etc.