This study explores the limits of technological substitution in traditional craft production by examining which processes in Yazhou pottery are considered irreplaceable by artisans and why these boundaries persist amid ongoing technological transformation. While existing research on intangible cultural heritage (ICH) increasingly emphasizes modernization, efficiency, and technological integration, comparatively little attention has been paid to the processes that practitioners actively resist automating. Drawing on semi-structured interviews with master potters, young craftsmen, and design professionals in Guizhou, China, this study conducts a qualitative thematic analysis focused on artisans’ experiential judgment, embodied skills, and boundary-making practices. The findings reveal that key stages such as glaze control, firing judgment, and surface finishing are widely regarded as non-substitutable, not because of technical infeasibility, but because they rely on tacit knowledge, sensory perception, and situational decision-making accumulated through long-term practice. Artisans articulate technological boundaries as a form of cultural protection, selectively accepting mechanization for auxiliary tasks while reserving core aesthetic and material decisions for human expertise. This study argues that irreplaceability in craft production is not a static attribute of techniques, but a socially and experientially constructed boundary shaped by cultural values and embodied knowledge. By foregrounding what cannot be automated, this research contributes to intangible cultural heritage studies by shifting attention from technological adoption to technological limits. It offers a conceptual lens for understanding how artisans negotiate modernization without relinquishing cultural authenticity, providing insights relevant to heritage governance, craft sustainability, and debates on appropriate technology.