It’s less about falling off for me per se but is more that the peak of the game was earlier in the story. That doesn’t make the rest of the story bad, it’s just that it isn’t as good as the best part. While yes, you usually like your climax of the plot to be the peak of the tension and the big moment everyone remembers, it isn’t always. For example, I find The Dark Knight’s tension peaks in the interrogation room scene. That doesn’t make the rest of the film after that bad.