He's full of it, cause I read The Martian and it definitely has a line at/near the end that is promoting working together toward a common good (which the movie leaves out and exchanges for a bootstraps individualist line). With how aware of ideology I am these days, it was very obvious to me when I read the book vs. watching the movie, what they were doing, replacing even a mildly collectivist message with an individualist one.

I could easily believe Weir wasn't consciously writing it out that way in the book, but it doesn't change the fact that works of fiction have ideological messaging in them either way. You can't avoid it by pretending you're "just an entertainer". You'll still insert bits of stuff you picked up from others, and bits of stuff you believe in, into what you write.

People who say this stuff about "preachy works vs. works without commentary" are some of the more oblivious to propaganda (or they are lying). Preachy works aren't more ideological; they are less covert about what ideology they are promoting and are sometimes more pointed in promoting it than unconsciously written works. That's the difference. But Andy Weir is a Yankee white dude, so it's easy for him to think that the dominant ideology is "common sense" rather than ideology, since it benefits him.