I think the story of the suppression of the idea of evolutionary progress has to do with political correctness. Ever since Darwin wrote "Never say higher or lower" in a notebook margin, evolutionary progress has been a hot potato - because of the political implications of some individuals or groups being 'higher' than other ones. Many humans have a sense of egalitarianism; they favor equality, and strive to create it where it does not exist. Evolutionary progress conflicts with the idea of egalitarianism in a number of ways - by denying that equality exists, and by casting doubt on the idea that equality is desirable. In the face of this conflict, many keep their egalitarian ideas and reject the concept of progress.
For me, this seems like a fairly common situation. Political correctness says one thing, and scientific truth says another. Racial and sexual equality run into the same problem: science says one thing, political correctness says something else and then the humans get their panties in a knot.
Evolutionary theory doesn't do equality. The whole idea of evolution is predicted on some creatures doing systematically better than other ones. Cultural evolution compounds the problem - by proposing that differences between humans can arise as a result of cultural transmission - and so can be very large.
The link to political correctness doesn't seem to be much of a secret. One of the most famous proponents of denial of evolutionary process was Steven J Gould. Gould made no secret of his Marxist tendencies.
The influence of political correctness on science is an insidious problem. As we race towards an era of intelligent machines, it becomes increasingly important to have accurate models of our situation. Massive wealth inequality mocks our preferences for egalitarianism. Humans will face increasing cognitive dissonance as their superstitions conflict with the facts.