Getting the likes of Robert De Niro, Morgan Freeman, Michael Douglas, and Kevin Kline in one film should be a recipe for a rousing success, and in many ways throughout Last Vegas, the casting is very successful. The main cast gives everything actors can really contribute to a film, and they excel as well as they can with what they're given. But the film shows that, at the end of the day, the script is king, and Last Vegas falters because its dreadfully weak writing hinders some fun performances.
Like another Vegas comedy, to which comparisons are unavoidable, the film centers around a bachelor party. Billy (Douglas) is trying to hold onto his youth with the grip of an iron vice. He's engaged to a much younger woman and decides that his wedding is the perfect time to rekindle his relationship with his three best friends, a group friendship that has frayed over the years. Archie (Freeman), Paddy (De Niro) and Sam (Kline) pack up to experience a weekend full of geriatric high jinks before Billy's wedding. Each of the four characters travels to Vegas with a certain amount of baggage stowed away in the carry-on compartment, and it's all related to aging, but the resolution to all of these character threads ends way too predictably. The first resolution to each of their stories that swirls around in your head while watching will undoubtedly be the one that pops up on screen before the credits roll.
One of the biggest sins Last Vegas makes is that it's just not all that funny, and the problem lies in the script. The film seems content with telling the same joke about old people over and over again, ad nauseam. It can barely mine humor from any other source besides the characters' advanced ages, pounding that theme into your head like a pulsing jackhammer. Jokes are fired at a machine gun pace, but so many of them fall ridiculously flat. Even when the cast is able to sell some of the feeble punchlines, they still aren't very clever or memorable. If anything, it makes it clear to see why these actors are as celebrated as they are. They all posses a serious amount of charm that bounces across the screen and makes the duds clank a little less loudly.
In fact, any enjoyment to be had from Last Vegas stems solely from the performances of the principal men, and sultry lounge singer Diana (Mary Steenburgen). All five actors possess a natural chemistry that carries the film's limp material around long after the script has forgotten how to be clever. They all have an excitable energy that permeates the rest of the film, but energy means little when they aren't saying anything particularly interesting. During the film, you're never quite bored or offended, but you're never excited either. It just chugs along in a miasma of general competence but not much else.
Last Vegas isn't quite dead on arrival but it's no a spring chicken either. Its high points ride on the backs of its stars' finely aged charisma, and much of the pleasing aspects that exist in Last Vegas would still be intact if the film just consisted of the actors sitting in a room, chewing the fat with each other without a script or direction. At the very least, they would have fewer stupid things to say. What happened in Vegas probably should have stayed there.