What is the point of wardens apart from a nice title for king to use in feudal politics? Whenever there’s an actual war it always seem to be the king, hand or a knight of the Kingsguard leading the forces.

I don’t think that’s accurate. The Wardens were activated for the War of Ninepenny Kings and led significant forces, Ned as Warden of the North was one of the leaders of the armies in the Greyjoy Rebellion, Harlan Tyrell and Lyonel Tyrell were both army leaders during the wars with Dorne as Wardens of the South, etc.