Counterargument #1: it might be better to incentivize people to run actual companies that deliver business value.
Response: there is so much value to be created that is hard to capture via current market structures. There are many people passionate about things that fall into this category.
Counterargument #2: AI obsoletes creation of cool stuff on the Internet.
Response: on the contrary, in many possible futures (esp. with constraints on agency), AI empowers people to deliver beauty to others, by automating all except the things they are passionate about. Motivation becomes more of a bottleneck.
Also, these types of public goods are some of the things that make me most proud of the current human civilization. I’m sure many here will agree. Even if we lose that in the future, I think it still matters, even as some sort of nod to the things we used to value in the past.