Pennywise was very inconsistent
He can go from attacking and dismembering a little boy one moment, but attacking another's face and it not do any damage the next. He doesn't hesitate to come into Beverly's home and take her after she attacks her dad, which seems a strange time to me as she just proved she overcame her fear of her dad, which the clown disguises himself as later on to attempt to frighten her. But in many other instances he's happy to creep up on the kids when they are all alone and let them get away.
The fear aspect serving as somebody's vulnerability seems very inconsistent and poor Georgie probably had the worst luck of anybody.