Warning: No spoilers, but this is a long review, but I think it's quite comprehensive and considers a lot of perspectives.
Overall: Not amazing but solid movie just as an action movie for entertainment if you don't mind cliches too bad.
Pros:
The visuals are stunning. Everything looks great and it's all very impressive as most reviews will say. I thought the acting was great in several instances, and Hugo Weaving in almost all of his movies always does great in my opinion.
The plot is really interesting, to me at least, although I tend to geek out about books or movies based on books that have a decently large "universe" to them (ie. Star Wars, Harry Potter, Lord of the Rings). Heck, the Dark Tower movie was also harshly criticized and had a bad rating but I thought it was a solid action movie just as an action movie. I also ended up reading a lot on the book series as a result of the interesting idea at least (and probably gonna do the same for this book series). I see this as very similar movie, where, say what you will about the pace and writing and what not, this movie is a decent action movie in terms of straight entertainment or visuals, and has an intriguing concept even if the execution in terms of storyline in the movie is questionable. If you don't think about it too much, it's just great as a source of entertainment and isn't that what movies are for?
Cons:
Of course (and a lot of reviews will say this), there are some large problems with this movie. Many plot points are predictable for people who have seen a decent amount of action movies (for those of you who have seen this movie you know exactly what I mean). However, with so many movies out there it is hard to be that original. Of course, those few truly original films are amazing, but most films have at least some parts that can be argued as derivative. So if you, as a movie-goer groans at every cliche big or small, then most movies will probably disappoint you now. Mortal Engines had perhaps a few more than most, but it mostly is made up in terms of visuals and the interesting concept. If you don't expect too much in terms of being totally original, and just watch the movie for the sake of entertainment and appealing visuals, then it's a totally fine movie. Although I haven't read the books, I've read up a bit on them and I will continue to, and I just feel like for such an expansive, intriguing and amazing book series, it's understandable that the writers wanted to fit more things in (since there are so many interesting things, and also maybe to appease the fans who read the books and expected certain characters). However, it does create that common sense that "ah someone died whatever, I just got introduced to them 5 minutes ago". And some parts seem to be lacking and what not. But hey, again, take the movie as a fun entertainment movie and don't be disappointed that badly if there's bad character development or cliche character development because these things happen so often nowadays in films.