1. No idea how to write a screenplay.
It's arguable over whether Tucker Max is a good writer or not, he is however successful - and for many people that alone is their measure of how good he is. Reading through the final script there is a strong sense that he, and Nils Parker, do not know how to write a screenplay. There are witty asides within the script that cannot be replicated on screen. For example
"The group laughs as we ANGLE on Jeff, 24, a thick-necked, ex-high school athlete that no one has ever accused of being a nerd"
That's just dumb.
On top of that, whilst it reads well - just like one of Tucker's stories, there are so many lines that can't be delivered because they could only be funny as they exist when written down. Tucker Max doesn't know how to write genuine dialogue because he's so used to writing it in a way so that a story will read well.
The dialogue between Tucker and his two friends clunks back and forth as though it was formulated by a 15 year old. Jeff refuses to go to the strip club because he has wedding arrangements that he must make, but after one sentence of "It'll be the greatest ever!!" from Tucker, he's suddenly convinced and just as motivated to go.
Many characters' dialogue doesn't match their motivations. It's disjointed as hell.
2. Too many clichéd/hypocritical moments
So many of the jokes are lame and cliched. There's the lowly janitor at the diarrhoea hotel who (according to the script) HAS to be a Mexican. There's the scene where Tucker makes fun of a fratty college guy in a bar and chides him by saying "I bet you even have one of those stupid frat rat names, like Chance or Reed."
Are you FUCKING KIDDING ME? A guy called TUCKER is ragging on someone for having a stupid WASPy fratty name? Fuck outta here..
There's the scene where Tucker takes the mic at the wedding reception from a bumbling best man in order to deliver his redemption speech.
The scene where Aaron plays with the child of a stripper, and the child helps melt his hateful heart.
The bride-to-be's parents are staunch Baptists whilst their daughter is loose and carefree. She's totally cool with Jeff heading off to a strip club, she just wishes that she could come too - isn't that RAD?
Plus, there's the obligatory guest appearances of the fart joke, the shit joke, and of course a starring role for the big beefy friend that will beat up anyone that comes back at Tucker for being a dickhead.
3. Poor characterization
It seems like every character in the film exists purely to be a strawman for Tucker or Aaron to tear down verbally. A character enters scene, receives a verbal beatdown, and exits stage right without coming back. This stems purely from the poor screenplay writing I mentioned earlier but it hurts the quality of the script so badly.
In so many scenes, women exist only to receive a joke at their expense to which they either leave in disgust or stutter a poor rebuttal.
However, it is the main three characters who are the worst victims of the poor characterization. Having actually been Tucker for thirty-something odd years surely he would have able to write himself with more qualities than the singular overbearing, raging dickhead element.
One of the most famous qualities that Tucker Max aspires to is out-and-out narcissism. In real-life, people like this are a fucking pain - but on film, it's captivating. Take, for example, the character of Captain Jack Sparrow from the Pirates of the Caribbean trilogy. He's probably one of the most recognisable anti-hero figures in Hollywood history purely because he totally and utterly believes in his own hype. He glides through every scene on a wave of his own self-confidence. As a result, he drinks alot (which makes him even more confident), is a bit of a cad with the ladies and is incredibly witty. The Tucker Max character clearly aspires to his level of narcissism.
Unfortunately the script is written with this purely in mind, everything the Tucker character does must be as awesome as scientifically possible and as such each scene is written to force this point home. In PotC, Jack Sparrow actually seems to exist as he is, in the world, and his reactions to everything are the reactions of someone who is a narcissist. In IHTSBIH, the whole world seems to exist purely to revolve around Tucker, to set things up so he can knock them down, to prove that he is a narcissist.
You might disagree here, you might argue that Jack Sparrow was written the same way. But in PotC his character had redeeming features, he believed in his own self so much that he grew to become an attractive anti-hero - here, in Tucker Max, we have a character with no redeeming features at all who must have his own redemption tacked on at the end, almost as an after-thought. His character has no drive, no attraction, there's no reason his friends would want to be friends with him, there's no self-growth story arc, he finishes the movie the same way he started it - a dull two-dimensional character.
5. Painfully generic
It is really nothing that you haven't already seen before. You've seen this film done as Bachelor Party, Old School, American Pie (the ones that went straight to DVD that is) and Road Trip. The only difference is that it's not really that funny. It's a mish-mash of events that happened in the IHTSBIH book, stuff that happened after the book, and an entire scene based around a piece of prose that Slingblade/Aaron wrote about the McGriddle on the Tucker Max Message Boards. If you are a Tucker fan, you have heard EVERY single joke in this movie - it's clear that Tucker had a massive amount of writers block, probably the reason we've yet to see Assholes Finish First in stores.
Almost all of the few funny scenes are quotes that originated from the Slingblade character - i.e. stuff that Tucker didn't come up with. The McGriddle dialogue, one notable scene of snappy dialogue with the sassy stripper, one or two other lines scattered here and there.
This is a movie that all the fanboys think will "revolutionize the genre" - the cast and director are going to have to pull out a miracle to turn it around, as the script is so stale, the characters so bad, and the dialogue so fucking shit - that it will amaze me if it gets a theatrical release.