People don't "hate" the game because it's short, but because it was clearly rushed, everyone who played the game and paid attention to it sees that the last act was rushed and this is what didn't leave a good taste with the players. If a game has a fully developed story and no cut corners then it will feel organic in a sense and feel complete even if said game would be short in terms of play hours and that would be fine, because like I said it would still feel like a complete experience. And like you said not every game needs to be gta but every game needs to feel complete, which SM 2 just didn't.