The idea of an open world has always been appealing to gamers and game designers alike. (An open world game is defined here as a game in which the player can move freely about a map, choosing how to go about achieving certain goals.) The idea is so appealing, in fact, that one may easily find it in a game where it does not belong. For example, action games: games of hacking, slashing, and shooting in which the player is essentially a tank, really only challenged by either a sheer amount of enemies or a particularly difficult boss battle.
Open worlds have a detrimental effect on this style of game for a number of reasons. Firstly, the nature of open worlds best accommodates RPGs. The player can venture down a variety of paths in order to advance skills according to whichever approach they prefer to achieving goals, ultimately feeding into their overall play style and sense of engagement with a game. Action games place more of an emphasis on the physical challenges related to hand-eye-coordination and the like, and when this concept is juxtaposed with an open setting, the "choices" presented to the player feel shallow and shoe-horned in. The way a goal is always achieved in this style of action game is through brute force, and powering up preset abilities in order to advance that notion does not feel like effective choice-making.
Example: 'Castlevania: Lords of Shadow 2'
This example comes as more of how the promise for the game was not executed in its final form. In Castlevania: Lords of Shadow 2, the player is able to navigate between levels seamlessly (without transition), and given choices on how to progress (or so it was promised). This RPG element feels out of place, however, as the only things the player is able to advance in regard to allotting experience points earned are predetermined abilities and weapons. Instead of a vast array of decision trees ultimately ending on an at least somewhat customized character, the leveling structure is very linear. Every play of the game will be strikingly similar if not identical. This cheapens both the action and RPG components of the game because it seems as if both are trying to distract the player from how bad the other one is simply by existing.
The original Watch_Dogs tries to be an action games first and foremost, putting aside its hacking abilities as a side mechanic, not the core. This makes the open world very awkward to go around as you just go around and take cover and shoot people, even though the world isn't designed in a way that makes sense for it.