To put it simply, you can't cram all of the exposition and detail of the first 13 episodes of the anime in under one hour and 30 minutes, that's why they need to get the best aspects of the material, with the author's permission of course, and make an enjoyable film. To put it simply, the division of the military is not that clear, the number of walls built were not explored and of course, the technology. Speaking of which, another thing that was pointed out prior to the release of the film is that it will differ from the source material for a lot of good reasons.
Now that I am done ranting about it being different from the source material, it's time for me to talk about the film itself and how it stands on its own. I enjoyed the film. Aside from reading some interviews of the film's staff, I also read some reviews of the film and I got to say, all I receive is mixed signals. Some reviews say it's good, some say it's decent, and some say that it's a really bad film. To put it simply, I have low expectations for the film both as a fan of the source material and as a movie goer. After watching the film, I realized that I should not compare it to the source material and I should watch it on how I watch my American superhero movies and TV shows, on its own merits. What I got is one of the best kaiju movies in recent years.
Unlike my usual Japanese superhero shows, it's more bloody and it focuses more on the human casualties and the terror these beings struck on mankind... just like in the anime! Even though the Titan action in the film is really great, there is one aspect of the source material that the film fails to deliver, the characters. Without spoiling anything, there were a lot of changes made when it comes to their characters. Some of the changes made include some of their character motivations and how they ended up in that state differs from the source material. Even if that's the case, the film gets the bare essentials of what makes these characters interesting in the first place.
As for the new characters whose sole purpose is to be casualties in this fight against Titans, they were... okay. Some of those characters I actually cared about while some of them felt like they were just there for the sake of seeing them die on screen. Even if some of them briefly appeared on screen, I was emotionally invested on those characters that I actually cared about. Why they failed with the characters? Thanks to the changes made to some of them, the interesting character dynamics between said characters were changed.
Speaking of things that went missing, the film barely has any 3D Maneuver Gear action. Yes, we see some of it in the film, and it captured the spirit and thrill on how we see it in the anime, but we barely see the Survey Corps use it in battle. As what the film implied, they were barely trained to use these weapons to combat the Titans. They know how to kill one using these weapons but it feels like they kinda forgot how to use it once they meet the Titans. Heck, the film features a lot of shots of them running away from Titans while they are wearing the gear, but only a few shots of them using it to run away from them. It's like the film forgot that all those who are wearing the gear are basically steam punk Spider-Men.
Considering that the best part about this film are the Titan scenes and how they all look like as well as how they terrorized the humans, it gave me high hopes on Toho's new Godzilla film that will air premiere next year, which will be of course, directed by the guy who directed this film. Lastly, will I watch the sequel, which will air next month? I got to say, I had a great time watching this film, so yeah, I will watch the second film.