Librarianship is constantly confronted with unexpected and quickly evolving sociotechnical challenges, yet the documents that define the core professional competencies for librarians are infrequently updated. Based upon survey responses collected from 383 working librarians located in the United States, we describe a set of gaps between current competency guidelines and current library realities with regard to practice, management, communication, career development, relations, and personal attributes. We argue that professional library organizations, educators, and policymakers could formulate more relevant and impactful core competency documents by deliberately integrating the on-the-ground insights of librarians' lived experience.