Boring, unlikeable characters, no humour whatsoever.
Every show, movie, etc. has one character that you genuinely dislike. This character is usually referred to as the antagonist. When the protagonist is unlikable, things start to fall apart for the audience, as we naturally want unlikable characters to get their comeuppance in the end, but aside from a few movies (Scarface), protagonists never do. When there are multiple protagonists, all of whom are incredibly unlikable, its nearly unbearable. Only two shows have pulled this off successfully. Beavis and butt-head, and South Park. There are two reasons for this. 1. The jokes are funny, so we focus less on the characters, and 2. The characters rarely succeed, and we can laugh at them and feel a sense of catharsis. In this show, not only are the jokes horrible, but the awful characters never get any sort of comeuppance and the few tolerable characters are always cheated in the end. Take the character Brian for example. He is selfish, rude, narcissistic, and even a bit sexist at some points. Its gotten so bad, that while watching the episode where he got ran over with friends, many of them actually cheered. Did I mention he's a dog? Seth Mcfarlane managed to make a DOG so unlikable that people enjoyed watching him be hit by a car. In the next episode or so, he is right as rain, never having learned any sort of lesson or changed in the slightest. Also, having watched McFarlane's other stuff, I worry that he is actually like this in real life. If you absolutely MUST watch this, there's not that much swearing or violence at all. Just don't be surprised if your kids turn into intolerable jerks after watching a few episodes.