I'm so glad you enjoyed it! I agree, it's a hidden gem that deserves more attention.

I still think 'you can't save Cath' would probably have been more narratively and thematically fitting

I can see the argument for this, but my feeling was that this theme was fulfilled by Mark accepting the reality of his mother's death. And not just that it happened, but that his acceptance allows him to get support from his friends and start to repair his relationship with his dad which was ruptured by the denial. I think the game tries to show that there are some outcomes you can influence and some you can't, and in either case how it affects you afterward depends on the story you tell yourself about it. (I also would have been upset to see Cath perma-dead, not only because I like her but because I get really bummed out by tragic endings for queer characters.)

I also really liked the ambiguity of the conclusion for Mark and Nicole. To me it underlined that there's not just one predestined "right" path through life, but many paths which could lead to many different versions of your life where you find happiness in different ways.

I'm sorry for the loss of your friend. <3