Tbh it's true that Kid's use of his devil fruit is really underwhelming when you know the kind of stuff Magneto and other magnetism users can do with their powers such as levitating themselves, creating magnetic shields, feeling the presence of each other via the small electric presence in each living being, turn mini metal objects into lethal weapons by throwing them at supersonic speed, etc...
It's kinda surprising given how creative Oda normally is when it comes to give powers to devil fruits.