Huh. I had not really thought Brave New World as using a feudal system but that really is what it is. It might be more accurate to then make the point that the vast majority of the other cases have systems that aren't just feudal but are ones in which the positions are inherited.

I agree that some of these writers are extrapolating. Since Asimov is explicitly writing in a world where the running theme is the ability to reliably predict social changes it shouldn't be that surprising that he'd actually try to do so. (Note also that Asimov also avoids here the standard trap of having protagonists who are nobles).