Ellie makes a mind bending mathematical discovery at the end of the novel that puts the whole story in an even vaster context. The movie skipped it. It's almost as egregious as Peter Jackson skipping the scouring of the shire.
In the book they send an elected representative group in the ship. She's gathering evidence at the end to confirm her story and persuade others that it's not a mass delusion (of which the mathematical discovery is a part).
In the movie Jodie Foster cries and says they have to take it on faith - basically the exact opposite of the book's message.
Except they don't have to... there are hours of static from her camera, something that should not be possible if she spent only a fraction of a second out of contact.
One way of reading the film is as an epistemological exploration of modern society and how one character evolves their belief systems in the face of both ordinary and extraordinary events. I love the movie far more than the book because it doesn't neatly resolve the "truth" of what Ellie experiences, and it leaves the audience, minus this scene, in the same place as the protagonist.
At around the same time, a group of religious NASA contractor folks I knew and had had faith conversations with where getting satellite imagery of Mt. Ararat. Those of us unbelievers somehow lacked "faith" but true believers like them were hunting for the Ark...
This is Sagan attempting to reconcile Ellie and Palmer, a dream of a scientific theology.
In Sagan’s book a scientist uncovers evidence that the universe was built and she’s working to leverage the scientific method to understand it. In that universe that appears to be what’s going on, but it’s the evidence that leads them in that direction.
I don’t buy that the “creator” cared about her feelings. In the book, the aliens she meets are just a more advanced inhabitant of the universe, they don’t know its origin either.
Religion usually does away with evidence to rely on faith based reasoning (which is basically what the movie does). The reason I don’t like the movie is it distorts the book’s point to be the opposite of what it was.