I thought K was probably the best iteration of the Replicant idea from the original. The thing about the Nexus 6 in the original was that despite their intelligence levels, they were essentially infants. Batty was only a three year old and he was the oldest of them. Their emotions were those of children and you could see how they lost control when emotional. K also was very childish emotionally in many of the same ways that Batty could be.
Again, I think if the film had tightened up and given more time to the culture of Replicants in this time period, it would’ve added more to the film. First of all, was there ever any mention in the original that replicants couldn’t have children? Even in this movie, no one flat out says that replicants can’t reproduce and, honestly, I kept thinking “is it that big of a deal?” Intellectually, I could see the problem, but emotionally, it never really mattered much.
However, if we had gotten more of the point of view of replicants as a subculture in the world that has to constantly be reminded to obey because they are essentially machines, I think it would have more impact. Too much was implied instead of actually shown. It’s a point where ambiguity was not helpful.
On top of that, I couldn’t really tell if there was some sort of racial distinction between the Nexus-8 and Wallace model replicants. Do the Nexus 8 hate the Wallace models or think of them as race traitors? Was the prostitute he meets and sleeps with a late model Nexus 8? If she was the same model as K, then wouldn’t she also have the same inability to disobey? How does K disobey when supposedly Wallace made that impossible?