DA2 gets hate because the main story was short, and the game constantly reused maps/areas/characters. It also has some of the most controversial companions in the series. You couldn't customise your character much at all besides having a different face and saying things in a different tone. Inquisition gets hate because the maps were too big and sorta empty, and the sidequests were boring as hell. The real ending was locked behind an expensive DLC. Oh...and the hairstyles, I guess. I don't see them get hated on for anything else, really...

Personally, I disagree with most of the complaints. Like, just playing the main story of all the games can make it extremely short. All the games have a habit of reusing old areas and maps...so again, I don't know what DA2 is singled out for this. I can see the customisation complaints, though...huge step back from Origins. I can also agree with Inquisitions side quest hate...most of them were boring. The hairstyles too...ick. But Origins also had the real ending locked behind story DLC(Awakening, Witch Hunt), but...no one complains about that for some reason.