I think a lot of us saw the classic trilogy when we were much younger, and a lot of us just accepted it unconditionally. Some of us actually go so far as to call them perfect. Now we are older, we know more about how movies are made, and we pick up on the seams in the tapestry Lucas is weaving with these films.
I really think a lot of the things people say are bad in the prequels, were also issues in the classic trilogy. Maybe if we were 20 some years older than we were when we first saw them, we would be picking apart the classic trilogy in the same way a lot of us pick apart the prequles, but we already accepted them into our hearts when our minds were much more open and now they enjoy a grandfather clause that keeps them from being subject to the same critical reasoning a lot of us use to condemn the prequels.