One other effect is much-improved manufacturing techniques. CADCAM, Numerical Control machining & riveting and laser alignment all contribute to a much more uniform product - sorry, aircraft. Whether that aircraft is good or bad still depends on the original design - CFD doesn't always beat the practised eye of a good Chief Designer.
Similarly active flight controls & sensor systems allow the aircraft's response (including stall) to be tailored to a much more uniform standard. It's common now to do check stalls to 1kt & 0.1 degree AoA on the first production test flight with no stall strip required.
The difference in construction methods & standards could not be better illustrated by the Nimrod saga in today's Telegraph. See
http://www.telegraph.co.uk/news/main...03/ixhome.html