There are several reasons for this.
The book is from Katniss's perspective. It's all first person, and you know her thoughts. You know her struggles, her fears, her loathing to kill, how she had to be the adult when her mother completely shut down for several years after her father was killed in the mine explosion, how the family had nearly starved to death, how the bounty from winning the games will give so many in her community a chance at survival and more, that they would otherwise not have.
Speaking of which, the movie really didn't convey just what winning the Game meant to a district, per the end of that last item.
The movie what drove Haymitch to drinking, and what really brought him out of it. Haymitch had been a Game winner, and then a mentor. But District 12 was so beaten down, that every year he invested his time and energy in trying to save two people from home, two people with no survival instincts or skills, who never had a chance at anything but victimhood, bloody sacrifices. Nor does it make it clear that once he saw the character and potential of Katniss and Peeta, he snapped out of it and put his all into helping them survive.
The movie doesn't really show just how dangerous the days after the Game were, not just for Katniss and Peeta, but for Haymitch and indeed all of District 12.
The movie just makes Katniss look like a pragmatist, differing from the pack of killers mainly in her lack of blood lust, and perfectly happy to fake romance with Peeta. neither is true; she was relentlessly forced into her actions by circumstances and her goal. She wasn't just fighting against (and she never killed if she had an option), she was trying desperately to save her family, her friends, her district. And Peeta, once she realized he wasn't the enemy.
If the movie upset you for reasons such as I mentioned, I strongly urge you to read the book before condemning the movie.
If the movie upset you because of its theme of government and media betrayal, I strongly urge you to read the book to better understand that theme.
No Listy lists were harmed in making this post, though they may have been offended at being left out. But, like a film maker, I have to choose what will fit. Sorry, Listy, you would have made my blog too long, and I didn't want to have to include an intermission.