The splitting-up of the Losers (the longest part of the movie) was IN THE BOOK

https://en.wikipedia.org/wiki/It_(novel)

"At Mike's suggestion, each person explores different parts of Derry to help restore their memories. While exploring, Eddie, Richie, Beverly and Ben are faced with manifestations of It (Eddie as Belch Huggins and childhood friends in leper and zombified forms, Richie as a Paul Bunyan statue, Beverly as the witch from Hansel & Gretel in her childhood home, and Ben as Dracula in the Derry Library). Bill finds his childhood Schwinn, "Silver", and brings it to Mike's."

This movie has a lot of critics and viewers criticising its length, but then again, the IT book itself was very big, and the "fetch quests" were in the book, and they were certainly meeting Pennywise separately even if they weren't collecting tokens. So why the complaints?