The reality is that we don't have AN Radio legs, NDBs in the lower 48 are almost unheard of and VORs are not being replaced as they need repair. HIWAS is also gone. If your aircraft is just flying for fun away from congested airspace and not too far from home, than none of that matters to you. For anyone else, however, some degree of modern avionics is all but essential -- when such devices are not required. This includes people like me whose airplanes reside in the DC SFRA. If I am just flying in the local flying area, I can mostly just make sure the transponders and radios are on, and use them as required. Most everything else is on, but not a part of my flying. The exceptions are traffic information (in the DC area, "see and avoid" is not enough for safe flight!) and a good moving map display (one or two) to ensure there is no inadvertent penetration of the SFRA or other restricted areas that are prevalent in my area. Could I remain clear by referring to paper charts and ground reference? Certainly. Do I want to be my certificate on it? Certainly not.

As Sam brings out, training and recurrence on installed systems are essential.