Tourism commercialization poses growing challenges to the preservation of authenticity in historic districts. Current conservation practices often focus on physical spaces, yet may overlook the integrity of “Scenes” as an integration of material and intangible elements, potentially leading to a fragmented loss of authenticity. To systematically quantify the impact mechanism of authenticity in historic districts, this study, based on the Scenes Theory, constructs a comprehensive analytical framework that integrates morphological indicators and social perception. Taking the Historic Urban Area of Kraków, Poland (including the Old Town and Kazimierz District) as the empirical case, the study combines the “Morpho” urban morphological indicator system with the OLS regression model to identify representative cultural scenes and analyze the intrinsic connections between facility configuration, activity types, and authenticity values. The results suggest that: Cultural facilities and interactive activities are core drivers of authenticity (Local, State, Ethnic); Commercial facilities exert a double-edged sword effect on authenticity—moderate commercialization facilitates rational perception, while excessive commercialization generates negative impacts; Residential functions play a positive role in maintaining the authenticity of the rational dimension. This study tentatively advances Scenes Theory as a spatial heritage management tool, bridges objective morphological analysis and subjective perception research, and offers preliminary actionable insights for differentiated conservation of multi-layered historic cities worldwide. The findings also highlight the educational potential of authentic cultural environments in fostering youth cultural identity, place attachment, and value formation.