Thats precisely why i say they shouldn't have doomsday or lex luthor in this movie at all, and go make a standalone superman v doomsday/lex luthor instead. Write doomsday and lex luthor out from this movie, remove the ** knightmare scene, remove the useless johnathon kent scene, then you got more than sufficient space for them to explore that aspect liao.
I cant say the opening scene is enough. they didnt talk about these to each other at all from the superman/batman perspective. Arguing about their different ideologies can also be seen as a "fight" figuratively speaking. can also show audience how both of them feel and respond when face with such ideology etc. can show more of their inner thoughts, emotions etc. superman told batman not to go to the bat signal, yet batman never question why. I think the writers of the movie know if say superman wanna fight batman because of the batman branding, is quite weak, so they use martha kent to give superman a stronger motivation to fight batman
Ppl say DC movie have to think and very deep, say marvel very shallow and just fight. But i think batman v superman like also no different. They make audience think not because it is though provoking, but because it is confusing one.