The conclusion of the last post raises at least three questions, and perhaps others.
First, something still seems wrong or at least incomplete with the picture presented. It is one thing to suppose that things can tend to improve. It is another to suppose that they can get constantly worse. You can count to higher and higher numbers; but you cannot count down forever, because you reach a lower limit. In the same way, insofar as culture seems a necessary part of human life, there seems to be a limit on on how degraded a culture could become. So if there is a constant tendency towards the decline of culture, we should have already reached the lower limit.
Second, if one looks at history over longer time scales, it seems obvious that there are also large cultural improvements, as in the history of art and so on. It is not clear how this can happen if there is a constant tendency towards decline.
Third, we argued earlier that the world overall tends to be successful in the sense defined here. The conclusion of the last past seems to call this into question, at least in the sense that we cannot be sure: if things are improving in some ways, and getting worse in others, then it remains unclear whether things are overall getting better or worse. Or perhaps things are just staying the same overall.
It may be some time before I respond to these questions, so for now I will simply point out that their answers will evidently be related to one another.