I probably just answered you elsewhere, but I'll leave it here to for others to read
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Of course it wasn't smart of Nic Hamilton to reply, but that guy is
very misinformed.
The studio didn't kick Fukunaga out. He chose to leave, because he wanted the film to be NC-17. He wanted to include a couple of sexual scenes. Not the ones from the book, but a few he came up with himself. The studio said no, and he didn't want to make the movie without them, feeling they were essential to the 'offensive' spirit of the book.
They are still using the Fukunaga script. The mentioned Chase Palmer was Fukunaga's writing partner on the project. Muschietti adjusted it a bit to his vision, and Dauberman only rewrote about 10%, some minor adjustments.
If you appreciate Fukunaga because you're a film fan, you might be familiar with the work of Chung-Hoon Chung. He's the director of photographer on It, so it's at least going to look very unsettling and very beautiful.
Muschietti's film Mama was alright. I like the atmosphere of it, the story, the characters. Script has some problems, obviously due to stretching a 3 minute short to a full length movie. With the tweaked Fukunaga/Palmer script It should be able to achieve greatness. Here are some comments from him, answering the worries of the studio going for a conventional jumpscare movie:
Now we patiently wait for the movie so we can see how it turned out