News like these are too vague to be taken seriously. It's the entertainment industry equivalent of "I heard it from my friend who's girlfriend knows a guy who knows a guy". So there are problems with the Superman script? We don't have any details on what type of problem "("major third-act problems" might as well translate into "ending not open enough for a sequel"), we don't know who said it, we don't know if it's what people working on the project think or if it's just that one guy. Adding to that, problems with production doesn't mean the movie is going to turn out bad.
I couldn't care less about the Superman movie, but this is ridiculous. We don't get to hear it because we need to know it or because it offers us any insight (on the contrary, it may as well offer us false insight), we get to hear this because we want to hear something and don't care what it is. Can't people for once shut up until they have something with actual substance to say?