I think that, in the most cliché reviewer-type comment possible, It Chapter 2 is really a victim of the first installment’s success. It Chapter 1 was a great piece of horror, with a great cast of child actors. The adult cast is also great, but by necessity they are to a certain extent doing impressions of the kids and tethered to those back-stories. Then there is a structural issue. In the book, I am told, the narratives are interwoven so events in the past and the future are happening more or less concurrently.
When they made Chapter 1, they decided to save all the really weird shit – ancient curses and burial rites and I believe in the book but it didn’t make it into the movie there is also a cosmic turtle – until the second movie. So, that basically back-loads the second film with a lot – like a lot, lot – of really weird stuff to sort out. And the final thing is the length.
This film clocks in at almost 3 hours, and by the end you can feel it. Part of that is because it needs to service this weird cosmic back-story, but I think part of it is also because the success of Chapter 1 made the director and the studio confident that, no matter how long the film was, they would be guaranteed audience buy-in. An untested property would never have gone for the 3 hour running time; someone would have forced some cuts at some point.
And someone should have forced cuts in this case. The movie is overly. And the other main problem is that there’s no enough of Pennywise in it. He shows up a few times, but there’s no show-stopper like the Georgie scene or the rotary projector scene. And in the end the film just degenerates into so much CGI non-sense like any other creatively bankrupt blockbuster you might see.
So, yeah. I think It Chapter 2 is still very enjoyable for the majority of its run-time, taking a brilliant concept and squeezing some more life out of it (I don’t think the adults’ story has ever been anyone’s favorite part of the book). But I also think this movie knew it was going to be a success and make money no matter what it did. So it stopped paying attention. And it showed.