Yeah. Didio has been quite open about his feelings on the most prominent members of DC's 30-something legacies, most directly with Nightwing.
On Nightwing in Infinite Crisis
And again in 2018.
He shot down
a few pitches for a Wally New 52 series (
Manapul tried hard to bring Wally back in cameo and was firmly told no) and pushed for
Barry's return in the first place.
So yeah, I know what we're working with and that whole mid-range of heroes, Grayson, Tim Drake, Connor, Wally, Kyle, Donna, etc, only exist as long as a writer of significant clout is willing to push for their return and continue writing them. (We only have Young Justice because Bendis pitched it.) Given his choice, Didio would rather have them gone to not age up the more "iconic" DC heroes. Tis what it is.
He didn't leave DC, he just stepped down from the CCO position for
a different WB deal. Jim Lee is the current CCO. Johns is writing and producing the GLC film, working on the DCU TV shows, and doing Shazam. He was also supposed to have a line of books under the Killing Zone banner, but those were
supposed to start in May of this year...