I've never seen an actual well-thought out technical argument on why decentralised social networks can't work. That's because there isn't one. People who are familiar with the technical issues surrounding this are humble and don't make bogus over-generalised statements like "X can't work [ever, everywhere, in all contexts]". This article is not a well-thought out argument either. It's a bunch of random irrelevant ane…
The problems I had with it I can't imagine being able to solve technically. It was merely not top-of-mind for the group I set it up for. They came for a little while but weren't inherently invested (e.g. you're "inherently invested" in your football team's communication mechanism. don't log in, and you don't find out about a schedule change). Instead it was just a group of friends I wanted to "facebook-verb-without-facebook-noun with".
Point is, Diaspora worked for me technically, just not socially. What was it missing in your eyes?