At afternoon tea yesterday, one of my colleagues raised the point that, particularly in Europe, the prefix neo- is automatically taken to be pejorative, with neo-liberal as the obvious illustration. It struck us that the corresponding, positively weighted prefix is post- , as in post-Keynesian, post-Communist and so on. 
My thought on this is it reflects an underlying progressivist assumption, shared even by many people who would reject explicit claims about historical progress. Given this assumption “post-X” is good, since it represents an advance on X, while “neo-X” is bad since it represents a reversion to X, implying the existence of some Y which must be post-X.
Feel free to provide counterexamples, contrary explanations and so on.