I think what I found convincing was that, despite it being a utopia, the people living in it were awful. I read it imagining myself living there and saying 'of course if I lived there, I'd be happy' but
they weren't, and the things that made them unhappy were so incredibly petty.
It's funny to see Nietzsche invoked in this context, since I'd imagine him giving much more weight to the slightly-more-ubermensch native MC than that of the society he clashed with. Nietzsche's a very subjective philosopher of course, but I'd imagine him saying that to love the world would be to refuse to engage with it in the glib way the society in BNW does.