The rapid growth in the development of Financial Technology has disrupted the private sector banking industry, introducing a new paradigm for digital financial services, augmenting the customer experience and ensuring consumer loyalty. Mobile banking, artificial intelligence, blockchain, cloud computing, big data analytics and digital payment systems are some of the technologies that have transformed how banking services are delivered by increasing convenience, accessibility and personalization for customers as well as speed and security for transactions. While there is a significant amount of literature focusing on the adoption of Fintech in banking, existing findings are fragmented and insufficient to form an overarching view on how customer experience can lead to long-term loyalty. To bridge this research gap, the current study systematically reviews peer-reviewed literature from 2020 to 2025 following PRISMA 2020 protocols. The study synthesized data from major academic databases using pre established search strategies, inclusion and exclusion criteria, and quality assessment procedures. Through this, the authors performed a systematic review of studies published before October 2023 to explore overarching research themes, theoretical background, methodological trends and new ideas in Fintech adoption, experience on the respective topics and relationship between private sector banking and Fintech. Results show that customer experience with a bank significantly improves through Fintech as it increases service quality, operational efficiency, personalization, accessibility, and digital convenience which in turn enhances customer satisfaction, trust, engagement, retention and loyalty. The review also mentions the ongoing challenges such as risks from data privacy and compliance issues, lack of digital literacy, adoption lead time across customer segments, and regulatory compliance and other factors. Moreover, the research points out significant gaps in existing literature that warrant further investigation, in terms of longitudinal studies, cross national comparative work and comprehensive frameworks to describe customer behavior in a digital banking context. Overall, this systematic review presents a synthesis of evidence published in the last five years on Fintech adoption in private sector banking and a set of recommendations for researchers, banking practitioners, Fintech firms and policymakers. The conclusion states that digital transformation can be sustainable if it involves a balanced ecosystem layered with technological innovation, security, regulatory compliance and customer-facing service offering in the truest spirit of banking to create long-term relationships & competitive advantage in future market scenarios.