I honestly liked it
Yes, it is cheesy in a lot of places but I honestly liked it. I'm a big fan of the manga and anime. The movie did alter the lore however, there was a lot things to cover in one movie if they wanted it to be exact to the manga. I personally feel the movie kept the core elements of the manga and worked from there to make a story that can fit into an hour and 40 minute movie. If you want a 1:1 copy of the manga, we have the anime for that. Having this movie doesn't lessen the manga, anime or it's followers. Enjoy the movie and take it for what it is, a cheesy monster movie that keeps the core of the franchise intact. Also, massive shout out to Satomi Ishihara for her portrayal as Hange, she was the best character adaptation in the movie.
This is my opinion, if you don't share it, that's fine. We all like different things.