SaaSpocalypsis is the growing belief that advances in AI have lowered the barriers to building software internally, creating an existential challenge for traditional SaaS providers. While the "build versus buy" debate has always existed, AI has dramatically accelerated the perceived feasibility of custom-built solutions by reducing development effort, cost, and time to value. However, software rarely fails because it cannot be built. It fails because it cannot be maintained, scaled, secured, integrated, governed, and continuously aligned to evolving business outcomes. In this new era, Customer Success becomes the moat against SaaSpocalypsis. Great CSMs move the conversation beyond features and technology to business value, helping customers identify the optimal solution for each stage of their journey, personalize adoption, prove measurable outcomes, and expose the hidden costs and risks of internal AI-driven builds. Instead of viewing AI as a threat, CSMs can reframe the AI conversation as a strategic advantage for both the vendor and the customer.