Kirsten Dunst looked close enough to comic book Mary Jane but her MJ acted nothing like her comic book counterpart. None of that energetic, spitfire, devil-may-care attitude was present in her MJ. So as far as I'm concerned, nailing down the characters personality and what makes them, them, is more important than whether they have red hair or blonde hair and to be fixated on details like that feels superficial from my pov.