To me the "if you like X read Y" format often fails because it fails to consider that individual readers like different books for different readers. I think the doorways framework is helpful in acknowledging these different dimensions.
For me as a reader, I have certain priorities and things that I liked in PHM.
I like that it's a story about sacrifice and love and teamwork.
I like that it's a story about hope in the face of terrifying adversity.
I like that it's a story about two people learning to understand each other and working together to save the universe.
I like that it's a story about two people brought together to solve a common problem, backed by millions of other people across the galaxy also trying to help (after all, one person, even a brilliant engineer like Rocky, cannot build a spaceship alone).
I like that even though the two main characters are basically platonic soulmates, they live in fundamentally incompatible worlds.
I like that it's a story about problem-solving, specifically scientific problem-solving that explains the science in a way that's understandable to me as a non-scientist.
I do like thinking about the logistics of long-term interspace travel.
I like that there's a ruthlessly efficient German lady making shit happen.
I like that Weir's writing is pretty solidly a 21st century style (I've read so much 20th century and earlier science fiction, I'm not trying to say that it's bad in any way, but if I'm looking for a readalike, the writing style is extremely important to consider for me).
I like how it's a story about first contact that is full of love and cooperation and sharing.
If you recommend me just any book set in space, or any first contact book, you're giving me a useless recommendation because those are some of the least interesting aspects of the story to me. For me, it would make just as little sense as a recommendation as if someone said "here, read this book after PHM because it also features a middle school teacher." I might like some of these other books that are being recommended, but because I like them for fundamentally different reasons, I just don't think it works as a "read this after that" kind of recommendation.
(I have read so many science fiction books, I wrote my undergrad thesis on science fiction books, please nobody interpret this as me not understanding or liking science fiction books)
