I suppose DC owns the character and can mistreat any way they please (as they do so many others). Captain Marvel is an adult. He's not stupid, just good-natured and maybe not cynical enough. I think this started with the 1970s issues of SHAZAM! which were so poorly writen.
In a way, the character now appearing in DC Comics is technically Captain Marvel, the writers and editors can make him jump through whatever hoops they like. You never know, maybe many fans prefer him as a child in an adult body. But it doesn't work for me.