Abnett added Remembrancers, who are journalists sent to document the glory of the Great Crusade. Nobody asked for journalists in 40k. I get that he wanted a human perspective but journalists? Seriously? I am here to read about muscular super soldiers conquering the galaxy and sodomizing aliens, not about journalists in space. Fuck journalists, TJD.
I like the Interex as a concept, cyber mechanical centaurs coexisting with xenos and having advanced tech better than the Imperium. But they are retards. They are supposed to be super against Chaos, and they were suspicious that Horus was corrupted by Chaos. So why did they literally take him to a museum where a super dangerous Chaos artifact was being stored? Wouldn't Horus try to steal it immediately if he was corrupted? And why the fuck was it sitting around in a museum in the first place for everyone to see? It should either be locked down somewhere secure or destroyed. Retards.
In Legion Abnett makes Alpharius fall in the dumbest way possible through the Cabal. He was given two choices, either stay loyal and have ten thousand years of stagnation, or go traitor and wipe out humanity and Chaos, allowing xenos to live peacefully after. Why would Alpharius trust the word of a bunch of random aliens he just met last Tuesday? And why on Earth would he prioritize the lives of xenos over humanity? Who's to say they aren't lying and just wanted humanity to fall and go extinct, because they are evil scheming aliens, and Alpharius joining Horus would accelerate it? Overall really stupid motivation for joining Horus.
The Perpetuals are all boring background characters that replaced the much cooler Sensei, and they do not fit into the plot of the Heresy at all. They completely disjoint any book they are part of, the main plot has to come to a screeching halt so we can focus on what these assholes are doing, which is often completely uninteresting. They don't really have a role other than to be Abnett's band of OCs. John Grammaticus is the worst offender, awful character meant to be the main character of the Heresy (Abnett's self insert) but ended up as the annoying Jar Jar Binks of 40k. And why did that Damian Brytannis guy kill MLK? Completely random fact that came out of nowhere in one book. Why mention that? Why did we need to know that information?
The Emperor now has a partner, Erda, whose DNA was combined with the Emperor's DNA to create the Primarchs. Sounds like a decent idea. You need a mother to have children. But now the lore has been retconned so she threw the Primarchs out into the Warp, not the Chaos gods. Because apparently she didn't want them to be generals and warriors? What? What else were they going to be? Gardeners? So according to modern lore, a woman ruined everything in 40k because she got irrational and out of control. Real feminist of you Abnett.
Dan revealed the Emperor's real name, we now know it is Neoth. Why reveal it? The Emperor should be mysterious, we shouldn't know his real name. It ruins the mystery.
Apparently Horus wanted to have a new Mournival with the Emperor, Rogal, Valdor and Sanguinius. He also wanted to create new Primarchs, and female ones too. Why? Why would Horus of all people want female representation in the Primarchs? "Father, the Primarchs have too many males. You are reinforcing the patriarchy. We must uphold equal gender representation. This is why I rebelled against you. The Imperium must go woke, father." Really nigga? Horus' whole motivation was he wanted a galaxy ruled by strong Space Marines and Primarchs over weak mortals, let alone women.