This case study proposes a novel framework, which aims to support UX designers and practitioners in the classification of identified usability issues. Existing inspection methods often lack in providing further information and steps about the effort to fix those issues. Therefore, the developed framework provides four categories for classifying usability issues in order to generate a score, which represents the present level of UX maturity. Furthermore, the score enables the comparison of UX maturity levels between systems with similar customer journeys, based on the identified usability issues. Results support system designers in their decision-making process of replacing, maintaining or modernizing the system in question. First results reveal that the proposed framework could be used as a meaningful extension of existing usability methods within different application domains, for instance the heuristic evaluation.