Someone in this movie mentions "Philadelphia Story". It's worth watching if you enjoyed "Failure to Launch", and it can can be said to tick a lot of the same romantic comedy boxes: beautiful people, aspirational lifestyles, characters who have difficulty with intimacy and commitment, family entanglements, mishaps with animals, pairings off at the end. It's my basis for comparison when I find "Failure to Launch" to be a bad movie. In the old days romantic comedies were written by "serious" writers, romantic comedies won Oscars, they didn't have to choose between being entertaining and being deep and meaningful. Romantic comedy is the genre with the most importance in our own lives, and Hollywood lets us down badly when hacks and marketeers write the scripts and stars phone in their performances.
Just a couple of things that I can put my finger on. If someone like me with no scriptwriting talent was writing this movie, and I wanted to show that even though the leading man looks like a bit of a playboy, he has the potential to be a committed and caring husband and father, I might think of having him mentor a cute kid and taking him to baseball games and stuff, and that would have comic potential because when the character needed to be told certain things, I could have the kid saying it and it would be precocious and funny and cute. But I also have to have something holding the character back from intimacy, so the last woman he was in love with died tragically, it's so romantic, it explains everything so neatly, and it turns what looks like a negative into a positive. Really, this is how bad the film is. You can make a million good romantic comedies out of answering these questions in believable and non-clichéd ways, and that's where comedy and character quirks should come from, not pasted on top in animal antics episodes. Somewhere in Hollywood there are writers who can do a better job than this, they just didn't bother hiring them for this movie.