Out of all the flaws listed, I have to say that the biggest one is trying to have it be a "Why can't we all just get along" anti discrimination story about how humans are mean to the poor ghouls who just want to be left alone to live their lives.
That's the entire premise of TG and it's just fatally flawed. And on top of that the author went out of the way to make a lot of the ghouls psychotic assholes who kill for enjoyment. Even supposed protagonist love interest Touka was going to murder a defenseless human girl just because she knew they were ghouls.
I actually find it unbelievable that they haven't declared martial law and called in the military to exterminate the very real threat of human eating monsters with superpowers roaming the streets.