It's baffling that Ubisoft thinks players would want to see this hero again, especially when the company says things like "he's older, but maybe no much wiser." Aiden is an absolute psychopath that has no limits and is unlikable in every way. Aiden was never meant to be a traditional hero, but even an anti-hero shows some level of awareness or regret about their actions. From the very start of the game, he's a gruff unlikable jerk, and Watch Dogs never makes any effort to show another side of the character. Equally frustrating is that players are never remotely given a reason to care bout Aiden. The biggest problem in Watch Dogs is that Aiden never shows any regret for all of the horrible acts he's committed, as he always just stays laser-focused on his revenge. Aiden isn't afraid to murder to see his mission out or invade the privacy of perfectly innocent people. He also puts countless innocents in danger, and probably kills some, by hacking traffic lights, bridges, and tons of other infrastructure. Aiden can steal money from anyone and everyone, even someone down on their luck that needs that money for medical treatments. His cold demeanor toward his sister is bad enough, but Aiden commits countless crimes across Watch Dogs, and the game simply explains it away as a means to an end.
The death is inadvertently Aiden's fault, but he never tries to own up to the mistake he made, and even just blows off his sister when she's trying to talk about her daughter. At the start of Watch Dogs Aiden's niece is killed by a hitman who was targeting Aiden himself, due to his vigilantism.
Aiden's greatest offense, however, isn't simply being a boring hero, it's the fact that he's a genuinely terrible person. Just at first glance, Aiden is a disheveled gravelly-voiced hero, the quintessential "hard" hero. The crux of why people don't like Aiden is that he's an unredeemable terrible person.