What am I missing here?

Rating: 4/10 (30 April 2018)

I'm an intelligent person who loves intricate movies that require lots of thought and, in some cases, repeat viewings to understand. The first time I watched this one, all I saw was an attempt at a horror movie that didn't quite work, though it did contain outstanding performances and had something to say about race. Then came all the awards and accolades, so I decided I'd better watch it again and try to look deeper. I've just done so, and it changed nothing. The plot still doesn't make sense to me. Why are the results of the "procedure" such blank zombies, and why would the perpetrators consider the procedure a success when such are the results? I've never asked anyone to explain a movie to me before, but I'd be grateful if someone would tell me what it is that I'm not getting about this one.