Imagination or spoon feeding?

Almost no background story was given for the witch and no way to kill her was ever explained. Do you like it when movies leave a lot to the imagination or do you prefer for them to lay it all out on the table for you? I personally prefer when I'm given the full story just because if I want to use my imagination I'd rather just read a book, plus the story just seems unfinished if there are a ton of questions left behind at the end.