I guess I am having a Dr. Manhattan epiphany here, but DC figures that, "Hey, I can make a statement as to which version of the character is best by killing off a character and the one left living is the superior one, kind of like killing Kal-L, a statement of him being the inferior one. Just a repeat of that now, the one who is alive is the better one because he is alive. TBH, in my headcanon, All-Star (Not One-Million), Kingdom Come, Red Son, and JSA - Thy Kingdom Come, just tell a more interesting story, to me anyways. I seem to notice, and find predictability, as to who and what the current regime preaches to me, and frankly, they pretty much made Rebirth 100 percent predictable in doing so, probably without even realizing it.
I just liked the guy from The Kingdom though, he didn't want some space-time continuum screw-up, but at the same time, wasn't willing to surrender the way things turned out for him.