I think "no child labor laws for the chosen one"/"forced to grow up too fast" readings of Captain Marvel/Shazam come from retconning Captain Marvel to be 100% Billy. Older readings have him as a separate but overlapping consciousness, almost like an imaginary friend.
OG Billy Batson, street kid, was for kids growing up through the Great Depression and WWII. At that point you've already grown up too fast. The power fantasy feels more about having an adult who could never leave you, never hurt you, never restrict your freedom or tell you what to do, but would always come when you called to protect you. Maybe I'm rambling but I feel like it's not really "what if a kid had to fix the world's problems" it's more "what if a kid had access to a Magic Word that meant adults and Gods HAD to help them fix the world when they asked. and also the kid got to go to space and meet aliens and wizards and cool things like that"