Agile methods were developed for small, co-located software teams, yet they are increasingly adopted in systems-intensive industries such as aerospace, automotive, defense, and medical technology, where development is shaped by scale, regulation, long lead times, and tightly coupled hardware-software dependencies. This thesis investigates the resulting discontinuity between Agile theory and Agile practice by measuring, for each of the twelve principles of the Agile Manifesto, both the importance practitioners attribute to the principle and the feasibility of enacting it under real operating conditions. The study combines a structured literature review with a cross-sectional survey of 68 practitioners and operationalizes the theory-practice gap through an Importance-Performance Analysis lens, complemented by a weighted gap metric and by one-way ANOVA across experience, project-type, and Agile-familiarity subgroups.