Against the backdrop of China’s booming affordable beauty market and the transformation challenges confronting local DTC brands, this study takes Brand X—a representative local brand that experienced explosive growth followed by a sharp decline—as the research subject, carries out an investigation in the second-tier city of Nanning, and examines the impact of the 4P marketing mix on consumer satisfaction, so as to address the literature gaps in regional market difference analysis and brand trajectory-specific research. Adopting a descriptive-correlational quantitative design, the study collects valid data from 385 consumers who purchased Brand X products in the past 12 months via a structured questionnaire, and conducts descriptive statistics and simple linear regression analysis using SPSS 26.0. The findings indicate that the overall consumer satisfaction with Brand X in Nanning is at a medium-to-high level (M = 3.711), with the place dimension scoring the highest (M = 3.743) and the promotion dimension scoring the lowest (M = 3.657); all four dimensions of the 4P marketing mix exert significant positive effects on consumer satisfaction (P < 0.01), and ranked by influence magnitude in descending order, they are place (β = 0.842), product (β = 0.787), promotion (β = 0.783) and price (β = 0.765); meanwhile, the core advantages of Brand X are identified as efficient logistics and convenient online channels, while its weaknesses include inconsistent product efficacy claims, a low-end brand image and uncreative promotion forms. This study challenges the traditional perception that product factors dominate consumer satisfaction in the beauty industry, enriches the contextual application of 4P theory in second-tier city scenarios, and provides actionable strategic references for local affordable beauty brands to achieve the development transition from “traffic-driven” to “value-driven.”