I don't know how the world described in the article is utopian. If anything, it's dystopian, in the vein of Brave New World.
It's a society where the VAST majority of people are happy. Really truly happy. A society that is in ecological balance with nature.
If Brave New World is a dystopia, what does that make the world we live in now? It has to be some kind of super-dystopia, because it's worse in every way you can possibly imagine.
The the society of Brave New World would fail as a utopia because of the "What would the Culture think?" test ;-)
It certainly plays the "moral" card, and more back when it was released. It FEELS dystopian because it plays at a different moral than ours. Oh, a world totally devoted to hedonism, with no families, everyone drugged all the time, where eugenics creates a cast system where people are clearly not equal.
Right now some of those things are less shocking than in 1932 (sexual promiscuity, for example), but Huxley makes a great work into presenting a good case on how the society presented WORKS and it is, at least, superficially a paradise. The book, after all, was written as a response to other "utopian" books that were describing "ideal societies".
I think that a lot of people, even today, gets a gut feeling that's a dystopia, and feel more identified with John the Savage, which is totally out of place and hates it. But I think that the genius of the book is that it presents a world that we can interpret as bad while their inhabitants live in bliss.
> It's a society where the VAST majority of people are happy. Really truly happy. A society that is in ecological balance with nature.
If you're locked up in prison, but the food is really, really good, aren't you living in a utopia?
The article says that the Culture intervenes in places that don't quite live up to their values or are otherwise problematic in some way. So if people leave the Culture and develop in ways that become unacceptable to the Culture and thus get interfered with again, how free are they to actually leave?
However, if you do go off and set up your own fascist dictatorship outside of the Culture there is also no protection should the Grey Area come hunting for you.
In practice, they mostly intervene against people with, like, slavery and death camps, not minor philosophical differences (or even pretty major ones; many civilisations run artificial afterlives of eternal torment for their people, and the Culture doesn't openly intervene against _that_). A number of breakaway ex-Culture cultures show up in the books, along with various Culture dissidents.
Key word: openly.