It’s more boring to have Batman kill again after seeing him murder for an entire movie and overcome it. It’s way more interesting to show him be the ONE guy on planet earth who still has a moral code during a friggin apocalypse.
The back and forth stuff is annoying not interesting. It’s like showing Superman mope for two movies, which actually works well enough once he resurrects in JL...because now you can see Supes arrive in his classic form for the second half. But if you then give us a JL sequel where he’s a evil, straight faced frowner for 3 hours...it’s like...why? We saw that already.
Let’s see Batman save humans even if it’s in a Knightmare timeline. We’ve seen enough of that other stuff.