If the human condition is not improving, either circumstances are getting worse, or they are fluctuating between some upper and lower bound. Each alternative is certainly arguable
Then there are those who emphasize that natural limits will keep the human condition within certain bounds
But, in reality, it is sometimes difficult even in the case of individuals to say whether changes have been improvements or not.
To evaluate the change in the person's state, we must treat the values of being content and being autonomous as commensurable, and some will argue that they are not