Bruce's entire MO is about generating shame and terror. Diana fights fear and stands for hope and second chances. Bruce is incredibly sexist and Diana's the ultimate feminist. Bruce loathes magic, Diana is magic. Bruce has faith only in himself, Diana is a priestess. Bruce hates and distrusts gods, Diana's been a god and remains a demigod. Bruce needs control and distance and plausible deniability, Diana gives of herself wholly and is only nourished by same. Bruce distrusts change profoundly, Diana's entire purpose is to change everything. Bruce is built out of deception upon deception upon deception, Diana is the incarnate Truth. Bruce loves and must protect Gotham, Diana loves and must protect her people.
They have *one thing* in common: they both punch bad guys.
"Opposites attract" may be a fun, trite little cliche to throw around, but birds don't fall in love with fish, and if they should try to live together, one of them dies. Bruce and Diana are incompatible on every level, and it takes a pretty good author to even make me believe they're the devout kind of friends they're supposedly meant to be. Lovers, never.