SAP Fiori and SAP SuccessFactors are two different but complementary technologies within the SAP ecosystem. SAP Fiori is a design and user experience (UX) technology that provides an intuitive, role-based user interface for SAP applications. SAP SuccessFactors, on the other hand, is a cloud-based Human Capital Management (HCM) suite specifically designed to manage the entire employee lifecycle.
SAP Fiori is not obsolete if you use SAP SuccessFactors. Rather, Fiori can enhance the user experience of SuccessFactors and other SAP applications, especially in organisations that need a consistent and customisable user interface across different SAP solutions.