I think that a marksman (small 'm') has a generic skill set which applies to the wider range of implements. That skill set becomes refined as specific equipment features and quirks identify themselves. Technological evolution broadens the skill set to apply better, as required, in dealing with specific implements. The marksman becomes better for those improvements. Without an adequate basic skill set, those improvements could tend to be wasted.
A day without learning may not be wasted, but it may not be beneficial, either.
The shooter is the unpredictable variable in the overall system of firearm, ammunition, shooter, and environment. This is because of the element of fee will. The shooter can choose, even unconsciously, to follow a set course of action, or not. Self discipline is the savior of the moment, guiding the shooter to adhere within a set course of action.
Often, it can be the failure of imagination which undermines the shooter's performance. For instance, many of us employ corrective lenses to refine our vision. Periodically, those lenses are replaced with ones produced to a differing prescription. Ideally, the shooter should refocus the eyepiece lenses of their rifle scopes to accommodate their prescription update. But do we?
Greg