This may sound like a hot take, but I've recently read comments (https://www.reddit.com/r/sitcoms/comments/1l0p7br/whats_your_most_controversial_sitcom_hot_take/) elsewhere (https://www.reddit.com/r/sitcoms/comments/1l0p7br/comment/mvf1n5a/) that initially, the premise of the show was just an average family sitcom (https://www.reddit.com/r/sitcoms/comments/1l0p7br/comment/mvfsmpe/) centered on a lovable dad. But after Paul Hennessey/John Ritter died (both on screen and in real life), they had to shift into a show with a real situation and have actual plot points.

In other words, Paul's death added an extra layer of emotion to the show. While parent deaths have been in sitcoms before, rarely have we seen main character parent to a young family die.