Before Social Networks, the web had all that, and it didn't work well. We had RSS feeds and Websites linked from the feeds. The reason Facebook, Twitter, Medium, etc. work well is because there's an owner who turns all the posts into a usable product. This owner is the equivalent of an editor of a journal or a newspaper. He decides what goes where.

The second thing that you do not consider, is that a publisher has a financial incentive, since he can make revenue from ads. Where is that incentive in decentralized social network? Who will care about making it good? Who will pay for developer's time?