The mere act of making a message accessible from an internet connection is only 1% of what "publishing" is, and it's the only reason Google, Facebook, and Twitter make billions. Otherwise, the whole Geocities-type model where everyone has their own private website would be successful today.
The reason these technologies are successful is that 99% of "publishing" is getting messages to the eyeballs that want to see those messages. The essence of their monopoly is that everyone's content they want to see is on that particular platform, both political and apolitical. It is difficult to follow people who get excommunicated from platforms, and the whole reason anyone uses these platforms is to avoid this difficulty.