Question: We learn in the film that Shazam and Wonder Woman are friends, and (Spoiler alert) she brings him back from the dead at the end. So, why didn't she help him during the final battle or give any other much-needed assistance during the film?
Answer: Where did you get the idea that they are friends? The movie makes it pretty clear they have never met before.
Cause they are having dinner together near the beginning. And you still didn't answer why she didn't help.
Answer: The other superheroes don't sit around waiting for someone to call. Batman has a city full of rogues' gallery: Joker, Penguin, Riddler, Mr. Freeze, Killer Croc, Catwoman. Wonder Woman also has the same. They're busy people! But they'll come if asked or if they find out another hero needs help.
Answer: The dinner scene, where Wonder Woman has the head of the Wizard, never happened. There's no indication they knew each other, let alone were friends. In the realm where superheroes actually do exist, there'd really be no reason why she, Superman, who is supposed to know them too, or any other hero wouldn't be there to help. So the only answer would be an unsatisfactory one that sounds pedantic: she didn't help because it's a Shazam movie and not a WW or JL movie. One could say that she and the other heroes were busy with fighting crime/battles in their own city or they didn't know they needed help. She only appears at the end, it seems, to restore the god realm. It's also been said they didn't think Gal Gadot would be available to shoot her cameo scene, so Wonder Woman may not have been in the film because of a scheduling conflict. But to me, if she was meant to be in the film, they would have secured her availability long before shooting.
Bishop73