Mobile ad hoc networks are essential for the operation of applications that require flexible, decentralized networks. The essential requirement for customized protocols tailored to distinct application needs is presented in this paper when examining routing improvement techniques for MANETs. Historical routing developments are evaluated in this paper, with a focus on application-specific methods that benefit different scenarios, such as energy efficiency and real-time communication. The impact of routing performance indicators is also evaluated in this paper through testing strategies such as adaptive algorithms and QoS-aware approaches. Security concerns, along with energy efficiency and scalability issues, are discussed in the paper before research directions are offered to enhance MANET performance under such dynamic conditions.