Airmanship is knowledge of the 'big picture' and where one fits into it. The more mental capacity one uses up with navigation, the less one has available for all the other important stuff such as lookout, listening out, aircraft management and communication.
I was brought up using paper charts and a stopwatch and was trained by the UK military system to fly at extremely low levels (day and night) to land at given grid references within fifteen seconds of a given time. I have always used the 'track up' method of holding a chart because that is the best way to orientate oneself when it comes to left and right. Turn up the wrong valley at low level in poor weather and you're a dead man.
These days I'm very happy to follow a magenta coloured line because it frees more brain cells and allows me more time to maintain a good lookout. I seem to spot most light aircraft long before their pilots have seen me, at least if said pilots do know and intend to comply with the rules of the air with regard to giving way to aircraft on the right, or the head on rule. I can only assume that some of those pilots who should have carried out the necessary avoiding action for my aircraft when they didn't have right of way are those with eyes pointing inside the cockpit for too long, looking at a paper chart, worrying about their next turning point.