The flying club where I got my PPL had restrictions on pilots with less than 200 hours total time. They couldn't fly the Mooney as it was a complex single with retractable gear.
Back then, with a CPL and 200 hours you were instructing or doing single engine charter if you were lucky. 1000 hours and an instrument rating got you into a Baron. With 2000 hours, the airlines would look at you.
The system wasn't perfect but generally the silly mistakes were made and learned from at piston engine level before you got onto the serious stuff.