Imo its less that people won't like a character that is "whiny", and more that it's unpleasant to be in someone's head who has a negative attitude. Most people are whiny sometimes. I think it can even be a good thing to have "whiny" moments or times unfiltered by positivity or even stoicism.
But when reading a book, you can put yourself in someone's head, and while there's usually value in seeing/being someone trying to bear up through suffering, generally pure rumination is not enjoyable or learnable-from. Imo the reader should get something out of being in the characters head, and that usually means two things: a positive, and/or, an interesting, experience.
I wonder if some very positive people might have a greater interest in it, for a change of pace.
But when reading a book, you can put yourself in someone's head, and while there's usually value in seeing/being someone trying to bear up through suffering, generally pure rumination is not enjoyable or learnable-from. Imo the reader should get something out of being in the characters head, and that usually means two things: a positive, and/or, an interesting, experience.
I wonder if some very positive people might have a greater interest in it, for a change of pace.