I think moral progress is a coherent concept, I'm inclined to argue no human society so far has experience it, though obviously I can't rule out some outliers that did do so in certain time periods since this is such a huge set. we have so little data and there seems to be great variance in the kinds of values we seen in them.
This is an Irrationality Game comment. (Though I'm actually not sure how it will score).
"Moral progress" simply describes moral change or value drift in the speaker's preferred direction. Very confident (~95%).
I thought it would be good to play the irrationality game again. Let's do it!