I thought Pennywise was very underused in the whole film, and the true version of IT was just a CGi mess.
The Ritual of Chüd was totally different to the book, I get that they couldn’t have done the battle of Wills in Space with the telling of jokes and the biting of tongues, but if they had introduced an element of something in the first film with the kids we could have got some of the mysticism across. Especially as the kids believe it.
As for the way they killed Pennywise, I get that the message is overcoming childish fears, but it was pretty lame, reducing IT to a baby like blubbering mess. I don’t think that was the best they could do.
In both parts I thought that it never really got across the camaraderie between the children. I didn’t think that it needed all the swearing and mum jokes and moving it forward to the 80s also made some things irrelevant. Why would young bill name his bike silver, as in all likelihood he would never have the cultural reference in the 80s. Speaking of Silver, I didn’t see a need for it in this film. In the book it was a huge part of Bills youth, saving him and Stans life in one instance, and then Audras at the end, yet only seemed to exist in here to get a King cameo.
Henry Bowers, no real need for him to be in the sequel. In the book he is released by IT as he can kill the losers no matter what, but this is not explained in the film. Also, in the book, he injures Mike so bad that he is in hospital when they go into the sewers thus reducing their strength even more, this doesn’t happen in the film, as Mike is the only character who knew how to kill him so has to be there, so pointless to have this small Bowers subplot.
I als think they could have shown the effects of the death of pennywise on the town of Derry. It pretty much gets destroyed by floods and storms, and given the relationship the town has with Pennywise it would have made his death a lot grander.
There are many many more things I could say but would take too long to write.
Personally I think the miniseries is actually superior to this, as even though it’s shorter it takes its time with the important stuff.
In chapter 2 it seems to rush into the return to Derry.