Gripping start, disappointing end

Rating: 6/10 (16 March 2020)

During the first 40-50 minutes, I thought the film was very interesting. The concept of a clone copy of the family and the mystery behind them and their existence was alluring enough to get you hooked into the film.
I found the dad's character completely unsuitable for the plot, however. He showed an immense lack of seriousness in many parts throughout the film, something that any logical person in that situation wouldn't do. For example, when the family was in the car and the daughter wanted to drive, the family got into a completely unnecessary and stupid argument about who got the most kills, and the dad talked exceptionally slowly as he explained how he got the most kills, all while 'evil daughter' stood there in front of them. This illogicality was not exclusive to the dad, but was most common in his character.
Now, when the plot started getting a little bit more complex (clones of other people as well), the film began to lose it's sense of thrill. What used to be unique to that particular family became common to every other person in the country, so it didn't feel so special and eerie anymore.
As the plot grew more 'complex', it started to quickly lose it's sense of logic. Those people were placed there intentionally? They spent their entire lives in that bunker? How did all of the people in the country (I will assume this is exclusive to the US from the antagonist's line "we are Americans") fit in that bunker? Surely after a failed experiment all those specimens would just be rid of? Why did they wait until the family came back to Santa Cruz in order to start their attack? How did the 'clones' suddenly became no longer linked to the original's actions and were thus able to conspire this?
And, after the final failed attempt at a plot twist, it appeared that our protagonist durings this film was in fact the evil version of the mom. When films have plot twists this major, they're basically telling the viewer "you didn't notice this even though the evidence was right there, we outsmarted you". And, sometimes, they get to say this. They have fooled us, the viewers, so well that you can't do anything but applaud. A successful example of this was the plot twist in Shutter Island, without getting into detail.
The problem with this twist is that it makes absolutely no sense. All the 'evidence' suggests the exact opposite. Why would the girl be traumatised if she knew what was going on? How was she inserted into the world as a 8-10 year old knowing absolutely nothing, and successfully pull off such a ploy? Additionally, if you noticed, all the clones could not speak English, or any language, except for the mom, because she had some form of foundation in English from her earlier life. However, this would mean that the one in the upper world was not able to speak English, at least at that point, yet she vividly remembers memories of her parents talking in English, meaning that she was able to understand every word.
This 'plot twist' was unnecessary, illogical and a very cheap and unplanned attempt at surprising the audience. And, while we're talking about that, so was the entirety of the last half hour of the film.
However, I feel like the film deserves credit for it's start and general idea. The cinematography and music was very well executed, and it was an excellent acting performance overall, but particularly by Lupita Nyong'o. I think the film could've gone way better, but credit where due.