Abaddon feels forced in a way that makes a lot of people just want him to fuck right off, I think. I kind of prefer the primarchs as background / legendary figures that are largely in the back ground, the more they are used the more their mystique is reduced. I think the problem with characters like Archaon and Abaddon is that they are introduced immediately as the biggest baddest dude with no build-up, no rise to prominence that makes them actually interesting. Not once have I met a fan of Archaon or Abaddon while pretty much every other special character has people who think they are cool.
Any Chaos warlord or character that usurps Abaddon's position would probably instantly become more popular as a result and pretty much all of them would make for a more interesting Big Bad Boy than Abaddon (he is the CEO's cousin so he needs a big role) the Despoiler. Hell, I do not like the Emperor's Children but I would be on board if Eidolon or Lucius took over. That would be interesting.
Personally, my favorite Big Bad Boy character is still Ghazghkull but I like characters that walk a line tween threatening and comedic.
Part of the problem is that abaddon isn't even a primarch, so wtf is he supposed to be doing compared to mortarion, magnus, etc?
The other part of the problem is that I don't think it matters if abaddon gets replaced, it'll be the same issue. Chaos can't get a significant win that actually matters, because everything in the universe has to be in a constant state of bullshit.
The imperium is a mismanaged and splintered dumpster fire that can't get its shit together to accomplish anything.
The eldar somehow haven't finished getting annihilated with as relatively few of them as there are left.
Drukhari are generally busy doing whatever CBT degen shit they do in between making fleshcraft sculptures and doing raids to get more people to make into sculptures.
Necrons consider humans to be ants they kind of want off their lawn, and are too busy infighting to do anything siginificant.
GSC are rabble that only exist as a means to make it easier for the tyranids.
Orks have to be dumb, or they basically end the setting due to being too prevalent if they ever get smart(which is why the war of the beast thing was dumb).
Tyranids if they could actually adapt as their lore says they could, should have overrun the galaxy years ago, and ended the setting more definitively than smart orks would.
So to keep in line with everything else, chaos has to be incompetent. In a way they're like the villain in a slasher fic, the only win the villain gets is because everyone else in the setting is borderline retarded.
