Intangible Cultural Heritage (ICH) emerges from the dynamics of change and continuity, woven through human experience and participation. The challenge in preserving and promoting this non-material culture lies in its inherently live, transient, and evolving nature. Contemporary art and design strategies focus on creating shared moments and performances that foster collective engagement. Experience Design (XD) along with its notable subsets, User Interface Design (UI) and User Experience Design (UXD), provide innovative methods to safeguard these cultural forms by directly shaping human experiences in both physical and mixed-reality (MR) settings. This paper studies visitors’ live and active participation in cultural spaces, like museums, galleries, and art/exhibition places enhanced by MR technologies. Aristotle’s Four Causes are applied to compare human participation in MR cultural spaces, with traditional spectatorship in theatrical plays as well as user experience outdated models like primal Human–Computer Interaction. By blending physical and digital spaces, the role of spectatorship transforms into co-creation, enhancing both aesthetic and educational experiences. Through case studies and examples, the research highlights the critical role of participatory design in preserving and promoting cultural heritage, offering new methodologies to engage audiences in immersive cultural experiences.