If you were offended or wrote this movie off because it wasn't up to your standards, you're not the audience this movie had any intention of appeasing.
In a movie filled with celebrity cameos and over the top CGI and humor, it felt to me like it was still a down to Earth movie they probably spent 30 minutes writing and had a blast filming and getting friends together and showed Hollywood excess from the point of view of the outsiders. It's a stoner comedy made by stoner nerd's that happened to find success and are probably just as baffled as these harsh critics are as to how they achieved it. A lot of these negative reviews I've read either have some kind of religious agenda against this movie or were people trying to measure how big their cinema knowledge penis is by citing great foreign films and comparing how much it falls short. I went in knowing how dumb it was going to be and found it really funny at parts and I liked the dark comedy eased with more immature slapstick comedy. I think too many movie-goers hyped it up in their heads that this movie was going to be the most epic comedy of all time.
I was actually surprised that it was better than I thought it was going to be.