The structural soundness of civil infrastructure is progressively undermined by factors such as deterioration due to age, excessive utilization, environmental pressures, and natural calamities. Strengthening interventions—once dominated by material-heavy, reactive strategies—are undergoing a transformative shift toward smarter, more sustainable, and digitally driven solutions. This analysis rigorously investigates the progression of reinforcement methodologies, transitioning from traditional approaches to intelligent and adaptive frameworks, with a specific focus on the assessment of structural performance, the incorporation of smart materials, and the integration of artificial intelligence (AI) alongside digitalization. The discussion expands into sustainable and circular approaches that align with global environmental goals, advocating for resource efficiency, component reuse, and lifecycle thinking. Finally, the paper explores forward-looking innovation directions, including AI co-design, 3D-printed retrofits, and bio-inspired adaptive systems. By synthesizing current research and future potentials, this review aims to guide the development of next-generation strengthening strategies that are resilient, adaptive, and environmentally responsible.