In Internet for the People, leading tech writer Ben Tarnoff offers an answer. The internet …
For such efforts to be successful, they must blur the line between technology's creators and its users, and eventually aspire to make the two categories indistinguishable. Expertise would no longer be defined in an exclusively technical sense: some people are experts in programming, others in design, still others in their daily lives.
— Internet for the People by Ben Tarnoff (Page 169)
This on networks of small cooperatives or non-profits replacing larger institutions.
I mean, this isn't exactly about FOSS, though in a sense it is. But I can't help but think that this is how FOSS is currently failing hard in most examples I can think of: it's rarely very friendly to the latter categories of people.
I struggle to think of making a system successful where programmers are users and vice versa, largely because I have a good idea of how much specialized expertise lower level programming requires. Even if at the user interface level, the UI becomes so easily and thoroughly customizable that programmers and users use the same tools and techniques, and are thus indistinguishable, it is likely that a level of abstraction or two lower, that is just not effective any longer.
Still, that's in a hypothetical complete system. FOSS often fails to even engage fairly with its user base.