That's an issue with editors not taking the magical side of the DCU seriously rather an issue with Ares himself.
As for why we should fear him, see the vision Diana showed in Perez's run where she finally defeated Ares. Or just look at how much chaos a god of war can wreak across the world in that run.
To the OP, the issue with Ares is DC doesn't take WW characters seriously outside of her book and that includes her villains. Personally, I'd make Ares a neutral character and replace him with Zeus, Heracles or Theseus as her main villain.