You made the claim that all cultures have changed the world for the better. To make that statement surely you must have some ground on judging what is 'better'. You set up a basis for cutural evaluation on the one hand with that statement, and then deny the concept entirely with your following statements.
"You set up a basis for cutural evaluation on the one hand with that statement, ..."
Nope - I said the world was better, I did not make any such comparision between cultures.
Unless you consider the world in total as a "culture" - I don't.