I recently watched this and I agree with you on most counts. The art was a little jaring especially for the men. The only voice I found miscast was Darksied. Andre Braugher is a fine actor and he hit his marks but his voice brings to my mind a sense of culture, civility and guile. He would make an outstanding Brainiac or Zod. He just didn't work as Darksied for me. Part of the problem I had with this movie it seemed like the first scene with Womnder Woman seemed forced and a little out of character. Attacking Superman and taking a member of his family without talking to him first? Thats a good way to get the guy with laser eyes to melt your f'ing head! Plus who better to teach a Kryptonian about her powers than The Flippin' Last Son of Krypton? It seemed like an excuse to just have her in the movie. Over all it seems like Superman was turned into kinda a pansy when Kara is conserned. Plus the fact that he believes her automaticlly and without question. Batman brodes, Supes worries, Wonder woman doesn't really do anything, Big Barda was awesome!
I totally understand what your saying. However, Wonder Woman's appearance in the movie was exactly how it happened in the book. I never understood why Diana thought she had a claim on Kara over Clark either. I get Clark being so damn giddy that he's not alone any more and wanting to trust Kara. I also understand that the more Clark trusts her the more Batman suspects her. ... You nailed it on the head with Darkseid also.
BTW ... if anyone's interested, my review for Superman/Shazam is posted on another topic. I didn't releveal any plot spoilers and left everything rather general/vague as to not ruin the ride.