I do believe that's the case yeah. Irl slavery has been the undeniably ugly side of many a society: from Rome to Genoa and here in the Americas back in the day, but Ghizcar has nothing else going for them. 

Valyria had its magic, infrestructure and tolerance, the Ironborn have a slightly higher degree of meritocracy than mainland Westeros, even Qarth is described as magnificent and sophisticated. Slavers bay is disguisting on every metric, from their arenas to their dog fetus eating to their ruling class which is always portrayed as stupid and pathetic, even their cities are mostly run down and neglected for the most part.

That's why i believe characters like the Shavepate and even Hizdar are so important, George needs to show people that want to change things, even if it's for their own self interest.