Have you ever tried having a long conversation with an elderly person, only to realize that they are bigots/homophobes/racists, etc? We all love Grandpa John and Grammy Sue, but they have to die for society to move forward. If there were 180 year-olds alive today, chances are pretty strong that a good amount of them would think that being anti-slavery is pretty progressive. They would have been about 90 years old when women got the right to vote.

We don't so much change our minds, and we grow new people and the old ones die.

Which hinges on "moral progress" currently happening or it being always desirable from our perspective.

A unexplored variant of the argument that I think works better would be one of the many examples of scientific revolutions marching on, one grave at a time. But obviously one could make a similar counter-argument that not all knowledge is good. Sometimes a better map gets you killed. But I would generally ignore that for now, since posters who question the high prior on the high instrumental value of a better map have a revealed preference of wanting a better map, considering the community they are a part of.

Edit: Missed this comment