Wire arc additive manufacturing (WAAM) has emerged as one of the most promising technologies for producing large and complex components due to its low cost, high deposition efficiency, and absence of size limitations. It is particularly suitable for Al-Mg-Sc alloys, which exhibit excellent weldability. This article provides a detailed review of studies from the past five years on WAAM Al-Mg-Sc alloys, focusing on metallurgical defects, microstructural evolution, and resulting performance. Existing researches indicated that in WAAM, optimizing wire compositions, process parameters, and introducing interlayer friction stir processing (FSP) can effectively reduce porosity, improve microstructure, and enhance performance. The lowest porosity was about 0.026%. Due to the strong microalloying effect of Sc, the microstructures were all equiaxed grains with an average grain size of about 10 μm. The alloys also exhibited excellent performance, achieving a highest tensile strength of approximately 470 MPa after direct aging, along with outstanding plasticity. However, the development of WAAM-specific Al-Mg-Sc wires, the mechanisms underlying metallurgical defect formation, the control of coarse and fine Al₃(Sc_{1 - x}, Zr _x ) precipitates, and the systematic evaluation of multi-property performance still need to be further addressed. Finally, considering the advantages of machine learning (ML) in the intelligent manufacturing, this review discussed its potential applications in WAAM, including forward performance prediction and reverse optimization of alloy compositions and processing parameters. Such ML-assisted approaches were expected to accelerate the development of high-strength Al-Mg-Sc filler wires, reduce manufacturing costs, and shorten alloy and process development cycles.