I think regular, mandatory retesting every few years for every driver should be done. It is kinda ridiculous that someone gets a lisence as a young adult and is just trusted to continue driving safely for decades to come.
Retesting regularly would help ensure more drivers keep their safe driving habits and stay up to date on the rules of the road. Yes this would come with a massive increase in operating costs, but it could save many lives from preventable deaths on the road.