That's not saying "oh TG copied AGK", that's just pointing out how bad the story is by being identical to AGK's.
Haise is just a small arc before Kaneki. Nobody gives a fuck about the half-assed "human ghoul" squad as their personalities are shallow and they are fucking irrelevant to the plot as a whole.
You're completely overshooting what TG is. It's not deep, it's not this intricate story, it's a bloody action series.
That creates a huge need for an antagonist or at least something of a goal.