I know that, and I know that I fucked up. This is not a good written ending, it could've worked if I set it up correctly, but I didn't and that is my bad. I lacked an experience on endings and how to do them, but DR was my experimentation game where I tested every thought that come across on my mind and the ending was one of them.Just found out about this game recently, and even though it's been done for a while now, I think I'll give my 2 cents; I don't think "bad ending" or "sad endings" are bad per se, it just depends on the feelings the story up to that point where invoking on the reader. This is something really hard to explain, since it's more "vibes" than anything, but people hate having control taken away from them in any fashion, so making them think your story is going to have a good ending and then not giving them that just feel bad. Good examples for these situations: Saya no Uta, Kara no Shoujo, CHAOS;HEAD, even Euphoria. The story makes it clear from the begining to the end that the story is not about a happy ending, it's about something else. Even with some light moments and some moments of hope sprinkled there, it's always obvious that things are gonna go bad. Of course, shock moments can be good, but not the ending. The ending is meant to wrap up what happened in the story until then, including the reader's feelings. Things can go bad in a story, but it needs to happen in the middle or the final moments of the story, not the ending.
I'm now well aware on how to do this type of ending, but I can't change it now. It's already out. I just wanted to give Serena a better ending by giving her a meaningful goodbye, but it didn't really work even though everything is all happy in the end, the execution leaves a bad taste in the player's mouth.