Welllllll..... thin is in for low reynolds numbers. But it tends to fail with higher speeds, bigger wing sections and higher wing loadings. What works for a bumble bee isn't what works for a fancy glassfiber sailplane and it's way out of the league for a Jumbo Jet. And then there's that pesky need for the wing to be thick enough to allow us to install wing spars of sufficient strength.

The closest we see to thin wings for an all around plane is in the fairly thin sections used on modern jet fighters. The wide chord allows a thin section that still can carry enough spar depth. The interesting thing with these wings is that the lack of high lift is so recognized that when the pilot pulls some amount of positive G that the wing responds by increasing the camber to a value intended to give the best lift with least drag. This means that the leading edge, flap and even ailerons all droop to give the airfoil a rather ugly shape that has more camber than usual for level flying. It's a horid looking segmented shape but it still works better than the thin and rather flat section.

They even flex to invert the camber for negative G loads.