"Dirty Grandpa" has collected in itself the absolute majority of intolerant jokes of different format. He mocks over old age, over youth, over blacks, over gays (over black gays too), over policemen, over doctors, over the institution of marriage and over religious beliefs. He makes it go, dirty, too frank. Occurring on the screen forces you to alternately close your eyes, then your ears, in fact, to stop laughing even for a minute. Why this happens is a mystery. You're right, the film, in general, does not differ in originality: for example, "American Pie" Paul Weitz came out more than fifteen years ago, and then again a bunch of times returned with his wits below the belt. Love intrigue, too, is in no hurry to impress the imagination: tales of student love and abandoned brides at the altar have long been smelling of mothballs.