Oh, man, Karl Marx would have just blown his lid with Foundation. Seriously. There are two kinds of people in Asimov's universe: those who control the masses and, well, the masses. Generally speaking, Asimov tells his stories from the perspective of those in charge. The masses are often considered at a distance, something to calculate, manipulate, and use to your advantage. When they do actually show up, it's often in mob form, never the best light in which to see the masses at work. With that said, the Foundation is said to have neither "peasantry" nor "nobility," and everyone has equal shares in society (II.2.10-11). So, we're left with some hard-to-answer questions. Is this a case of Asimov saying one thing but doing another? Is the average man represented in Foundation or does he lack representation? Are the masses and their leaders the same person? We may need to take this one slowly.
The role of the barbarous societies of the Four Kingdoms are more about building a Second Empire than about destroying the first.
The Galactic Empire was not an egalitarian society, so its destruction can actually be considered a form of progress.