Dart mixins provide a solution to the limitation of single inheritance in Dart by allowing developers to add functionality to classes without inheriting unnecessary methods. The use of mixins encourages code reuse and helps avoid method duplication across class hierarchies. In Dart, a mixin is defined with the keyword "mixin" and can be applied to classes using the "with" keyword, enabling a class to utilize multiple mixins. This approach is particularly useful in complex applications where extending multiple classes is necessary but not supported by Dart's inheritance model. However, excessive use of mixins can lead to violations of the single responsibility principle, difficulty in understanding class purposes, and long compile times. Despite these drawbacks, mixins offer a flexible way to enhance class functionality and manage code complexity, particularly in scenarios requiring multilevel or multiple inheritance structures.