That highlights one of the problems with Snyder as a storyteller and it's something I've said about him in the past: he answers questions nobody else asked.
His justification for the bleak tone in Superman, capping off with Superman committing an extra judicial execution, was that we needed a rationalization and explanation as to why Superman in the comics refuses to take a life.
...Was anyone but Zack Snyder really asking that?
Even now with the Justice League. All the talk about it was that it meant to cap off the arc begun in Man of Steel and how this would finally be the big birth of superheroism in the DCEU or whatever. Why? Why did we need to wait three movies (possibly four before they ditched the plan of making it a 2-parter like Infinity War) to see the superheroes actually acting like superheroes and not just dour sociopaths?
In addition to just needing a solid game plan instead of throwing everything against the wall and hoping something sticks, I think a major thing Johns needs to do is keep the writers and directors on tighter leashes.