Steam is introducing Achievement Sets, designed to improve the achievement earning experience

Steam has launched Achievement Sets in beta to enhance the achievement earning experience. This new feature allows developers to split up achievements and introduce seasonal ones. Specifically, Steam Achievement Sets will prevent DLCs from negatively impacting a user's 100 percent completion record. By providing more flexibility for developers and players, the system aims to refine how milestones are tracked and earned across different content updates and expansions within the Steam platform.