What Once Upon a Time in Hollywood could have really used was someone on set to tell Quentin Tarantino no. No Quentin, you shouldn't show multiple extended scenes from fake movies (and real movies) that don't really move the plot forward. No Quentin, your nostalgia for a bygone era isn't a good reason to make the audience watch characters drive around and listen to music for hours. I really like pieces of this movie, but I didn't enjoy it as a whole.