The joke isn’t that they’re cruel or bad at parenting or have any particular disdain for the world at large. They aren’t unkind to their neighbors or to the animals and their deeply devoted to their children and to each other.
The joke is that they’re happy.
The Addams Family is missing a lot of the typical sitcom tropes. There’s no mother-in-law jokes, no arguing over who’s supposed to fill what gender role, both Morticia and Gomez spend roughly equal amounts of time parenting the children and the most remarkable is the relationship between Morticia and Gomez. You see Morticia Addams and it really highlights how rare it is in family films and TV sitcoms to see a wife and mom character who isn’t like this “dissatisfied housewife always mad at my big dumb husband but I love him gonna stay with him because this is the world and he’s the best I can get and I am always right because wifes are the smart ones hey you can relate to this average American I guess”. Morticia and Gomez in contrast are usually working together you know rarely party A will keep something from party B but for the most part the form little schemes together as partners both are heads of the household and they almost never disrespect each other - remarkable in a genre where that’s usually the joke.
But the reason the Addams are happy is really beacause they exist outside of society’s expectations. Gomez is a man child who plays with his trains and that’s fine. Morticia fences with her husband and plays with weapons often and it doesn’t occur to them to care what other people think.