Hm. Maybe this film will give us a better sense of why the Federation banned genetic engineering. I never really got that sense from Space Seed and WOK. The augments were stronger and hardier, sure, but they didn't REALLY seem that dangerous... they seemed like humans with Klingon or Vulcan constitution. I'm loving the idea of augments being much more genuinely scary.
It's all in the subtext. The reason for banning eugenics doesn't really need to be spelled out in Space Seed or TWOK. The evidence of what it does to people is right in front of us: Khan. Besides, those really weren't meant to be a treatise on WHY genetic engineering on that scale can be bad. It relies on the audience to be able to connect the dots, and largely succeeds. The backstory is all in service of giving Kirk a worthy adversary.
It's different in the DS9 episodes involving Bashir and the other genetically modified humans, as those stories really did set out to explain "why this is bad."
It does represent something that modern movies (and modern storytelling) tend to do that really ends up being a disservice to the story: the constant compulsion to explain every minute detail about WHY the setting is the way it is. It's never enough to simply know "it is" anymore and let that fact guide the story.