Not trying to say there are no elements that are good satire within it, or that there isn't good writing at times. There is! I have enjoyed some 40k stuff myself, and it works well when the focus is on how terrible the imperium is.

What I am saying is that at large, in the big picture, it's really not doing it well. For every "Wow this is terrible." there's often a large amount of "Well, it's the best we've got." or focus on the heroism/glory/valor of Space Marine #39181. The IP is trying to double dip in tone, which ultimately is what lets the fascist fanbase fester. Because there are elements in the setting and content creation that specifically appeal to them, that appeal to their narrative and fantasies.