The thing is that, technically, "human fluorishing" (understood as the evolutionary tendency of our specie to thrive & expand) is not something that can be maintained indefinitelly. The experiments regarding behavioral sink show that when the conditions are overly favorable, those survival / thriving instincts don't play in our favor and nature tends to bring out all kinds of deviant behavior / unhappiness.
Sure, we are genetically predisposed to try and thrive as much as possible, but I'd argue a "real utopia" where humanity is "fluorishing" and at the same time "happy" is either unsustainable long term, or requires a very nuanced definition of "fluorishing" / "happy".