Utopia is not your average island for many a reason, but its social organization and hierarchies are probably the most obvious difference between there and, well, anywhere else. Often considered to be proto-Communist, Utopia depicts a society that seems to have almost no class-system, no hierarchies (aristocracy, plebs, etc.), and very rigid family structures. By imagining such a radically different conception of how people live together, More is thinking hard about whether everyone should have equal social standing or whether having some degree of social hierarchy is actually helpful. But wait, what's the answer? Don't hold your breath—More definitely doesn't give us one.
Utopian society isn't that radical; many aspects of its day-to-day organization are super similar to Europe.
Utopia couldn't exist without social hierarchies. After all, they are a natural part of how people live together. They aren't good or bad; they're just a reality.