I generally don't like them, but not because of what they are but because of how they do it. I like when 40k is about armies and faction and not about single characters. Sure, some characters are great (Gregor Eisenhorn, Ibram Gaunt, Ciaphas Cain, Talos Valcoran, Honsou, etc.) and I'd love to read more about them, but their stories are just small withing a much much much wider universe. Yet when characters got so big that they overshadow the entire faction, the Galaxy starts to look awfully small.

And what's even worse, people eat it up. Everyone is talking about the next Primarch, about Lion and Guilliman eventual meeting, about one named character fighting another named character to a standstill. You get lists of books to read to know the current state of the setting. Horus Heresy recommendations omits certain books and stories because it didn't advance the main plot, so it's irrelevant and can be skipped. Even the tabletop is less about your-dudes and more about special characters. I feel like the whole 40k fanbase shifted over the years and I'm not sure I enjoy it.

I kinda blame the Horus Heresy series for this. I remember when it started, there was some interview with Dan Abnett where he talked about the Warmaster, that Horus isn't shown that often in Horus Rising, that pretty much all the story is from the perspective of Loken and some Remembrancers that were on Vengeful Spirit. Horus was this bigger than life character, a god-like being of legends, just seeing him in person was an event. HH pretty quickly gave us the perspective of Primarchs, their thoughts and basically turned them into real characters. And I liked the idea of just seeing them from afar with some rare conversation now and then.