When creating a 'perfect' world/society, one of the biggest problems in my mind is the direct relationship between freedom and suffering. To create a perfect world is arguably to create a world without suffering, yet humans cause others to suffer by merely existing. However, suffering is also a necessary part of life. Without enduring past hardships, we would be unprepared to face any future adversities.
The Axiom (the giant spaceship) in the movie WALL-E is a useful reference when considering what a subjectively 'optimal' amount of freedom (and, by extension, suffering) could resemble. Inside the Axiom lies a dystopian society in which humanity is catered to by a myriad of machines and A.I.'s. Not only do the people living in that society not wish for anything more, they can't even begin to fathom what 'more' (as in, something worth working towards) would look like; after all, when their entire lives consist of their immediate needs and desires being a button press away, why would they? In short, the inhabitants of the Axiom are given little-to-no freedom, yet, somewhat ironically, they are free from suffering as a result. While the Axiom is one example of what a 'low freedom, low suffering' society could look like, other examples exist, many of which are far more extreme.
Ultimately, a perfect world would require the removal of what makes us human in the first place.
I had more to type, but I went to the bathroom and lost my train of thought. Well, not like it matters I guess.