Zion is a good player, and we all know he'd be a future hall of famer (If he keeps healthy), but the media is really hyping him up. There are actually a more deserving rookies and other young talents in that cover like Luka, Trae, or Morant.
I agree, I am not saying that Zion didn't deserve to be in the next 2k cover but there are good youngsters who prove more than him thus more deserving. Luka is a better option, everyone already witnessed his magic (already a superstar despite of a very young age) and I think that's enough for him to get such privilege 
. I am confused why they didn't pick him, hmm maybe he is less charismatic and less fierce than Zion?