The pure evil theme had been done a million times before.
It's old.
Sure it was new and exciting when Halloween first came out, but then came Friday the 13th, Nightmare on elm street etc
Zombie was just doing something new. Is that so bad? Would you really want to see the same thing over and over?
As for the crappy childhood, that's Zombies shtick. It's what he does. Look at Thousand Corpses, Devils rejects. Thats his style.