GPS is great for getting a position fix, an electronic version of celestial, it gives very accurate fixes.
Charts (datum, projections, updating, accounting for errors, etc), using fixed lights and light lists, sounds and sound signaling (horns, etc), compasses (and correction), dead reckoning, piloting (soundings, turning, logs, bearings), reading shoals and banks, fog, tides, currents, radar (reflection, refraction, ranging, echos), route planning, celestial (sights, reduction, time keeping, sextant use and maintenance), sailings, keeping watches, voyage plans, ocean state (waves, currents, ice), weather (reports, forecasting, routing, etc), weather monitoring (pressure, humidity, etc), etc, ... all that pesky stuff that goes under the heading "navigation", all of that stuff remains relatively unaffected by the fact that we can get a very accurate fix from a GPS receiver. In fact, Bowditch, the 800+ page "The American Practical Navigator" devotes precious (even worrisome) few pages to using GPS to get a very accurate fix. Said another way, knowing where you are at has very little to do with whether you are about to be run over by a freighter in the fog, or be swept on to a lee shore because the wind is clocking ...