I think the Vincent Price movie, Last Man on Earth, did a much better job of making the points you reference from the book. In that he ended up being the bad guy, unintentionally and unknowingly, and dying. It was a much better ending there.
In this version, AFAICT, only the alpha male is shown to have much intelligence. The rest are just shown as violent, hungry, dangerous animals. (alpha female doesn't count, she's basically out cold the whole movie). There doesn't seem to be a highly developed language they speak, just grunts and yells.
I'm not knocking your opinion or the book. I just think the movie doesn't resolve issues it creates with viewers who have no prior knowlege of the book or original story line.
Jack