Modern digital identity management (IdM) systems embrace self-sovereign and decentralised identities as core paradigms following user-centric principles. While the theoretical principles and technical specifications underlying modern IdM systems have converged, corresponding real-world solutions' adherence can be obscured by claims over design principles. To clear the fog, we develop a taxonomy for modern user-centric IdM systems through eight iterations of literature reviews and solution evaluations. To this end, we define the theoretical characteristics to achieve user wholeness, data autonomy, application usability, and the practical characteristics of the technology stack, architecture sharing, and system trust. This taxonomy contributes to a deeper understanding of modern IdM solutions' design and implementation decisions. We demonstrate the taxonomy's usefulness by evaluating five real-world solutions' adherence and capturing the diversity within the evolving digital identity ecosystem. We thereby enable practitioners and researchers to make informed arguments about which IdM characteristics best suit their specific needs and contexts.