So, does everyone hate watchdogs because it's not the best thing in the world? That's the only explanation I can think of. I played it, and I really like it. Sure it's a bit linear, and it sticks to a lot of the tropes of other sandbox games, but it's fun as hell. I'm seriously not getting why there's this big backlash against it.
It's the usual backlash against the hype that made the game look way better than it actually is.