Undertale in its heyday seemed to be groundbreaking in the sense that the ending of the game was dependent on the choices you made, but not in the sense that you think. You had a choice to be a pacifist, avoid conflict, be aggressive and attack everything, or be somewhere in the middle. Your journey would depend on the choices that you made and you wouldn't be able to change the ending of the game unless you started an entirely new save file. Was this why it was such a popular game? Why do you think it has died down? Do you still play it?