Ardent Prayer

The Wonder Woman theme is Wonderful.

The entire point of her in the movie was to be somewhat mysterious, and powerful when she finally came out. Fleshing out her character in this movie instead of waiting for the next would defeat that purpose.

Besides, you can't expect too many characters to be fleshed out. The amount of substance you expect them to have must be directly proportionate to the focus the movie gives them, and the amount of time they have within it.