Yes welcome to 2.0 or 3.0 chaos. The specific legions are gone but they have left enough leeway to build any legion any way you want. I dont see what the problem is. Its a redux of a codex, armies change as the always do when GW does a codex. Alot of what you hear is just whining from players, mostly newbs who havent figured out how GW works, quit crying, you should have been there when they ass raped us going from 2nd to 3rd. The only thing that changed in my army is I cant infiltrate everything anymore, oh well adapt and overcome. I did get back my 3 termy drop teams I used to love back in 2nd.
One thing I dont like is how they keep screwing with the fluff. Gone are the tragic hero legions that fell through nessessity such as the 1k sons and the Death Guard who were just trying to do the right thing and got screwed over by events. Also they totally screwed up my legion, the Night Lords who in the new fluff they claim went back to the Eye and sacrificed things to the chaos gods after the Heresy. BS, the NL dont worship chaos and look down upon any who do. After the heresy they waged on their own a guerrilla campaign against the Imperium for several hundred years leaving bases and hidden outposts throughout space before the bulk of them set up a main shop in the Eye. Even then they do not stay long heading back out to screw with the Imperials more often than they are in the eye.