I often wondered if this amount of effort is truly required and if it actually provides results people can relate to. I used Netflix for a while and I find the recommendations to be pretty average for me. Quite possibly it is because I don't tend to rate most movies I watch. I wonder how often that is the case for others though.
More importantly I just don't think you can predict what I want to watch based on factors such as history, ratings, watch times etc. External factors such as mood, recommendation from friend (not on Netflix) and curiosity almost always play a large factor in choose the thing I watch next. These things are not known to Netflix.
As a semi-educated guess I would say that simply providing a listing of popular movies based on ratings/watch times per genre as well as similarity would be enough for most people. It is easier to understand and how many people want to watch something just because it is popular anyway?