It seems to me that a utopia that goes into any detail is essentially a political argument – wouldn’t it be great if instead of doing this we could do that? Because it is perfect, there is no conflict unless it deals with outsiders. (E.g., Hogan’s Voyage from Yesteryear where the conflict is between the anarchist first settlers and the statist second wave.) A utopia that doesn’t go into any detail is just “wouldn’t it be nice if I didn’t have to put up with this stuff” – e.g. The Land of Cockaigne.
Consider a setting like Transhuman Space: there are plenty of places in it where people can live long and happy lives doing more or less whatever they feel like, at little risk of crime, etc.; but you don’t set adventures in those places unless something is going wrong. (Their existence, though, implies that PCs are either people who don’t fit into those places or people who can’t get into those places for some reason.)