Various reasons can be cited, but the biggest reason is that Marxism became less appealing and people are now skeptical about the significance of applying development stage theory to Chinese history.
理由はいろいろ考えられるが、最も大きな理由はマルクス主義の魅力が薄れ、中国史に発展段階論を当てはめることの意義を疑い始めたからであろう。