Sextant used during daytime (sun fix) produces a line of position, not a fix. To get a fix you must add DR, total accuracy from a small platform, lucky to get within 5nm. Running fix using map and compass from an aircraft, probably several nautical miles, direct map to ground immediately over a known feature, probably a mile. GPS accurate to 30 metres. I'll take the GPS thanks.
Map to ground gives you an indication what cross wind you have been flying in, glance at GPS and you get real time information, I'll take that thanks.
to get accuratE chart fix needs head focused inside cockpit, accurate GPS fix occurs with my head focused outside the cockpit, I'll take that thanks.
Flying down final, quick comparison between IAS and GPS ground speed then glance at windsock and you have a guide to expected wind sheer , I'll take that thanks.
Do I carry charts, you bet, I love them, they are fabulous for getting an overall perspective. Do I use my GPS, you bet.
which one is "primary", who cares! I use both.
peter