I'm not sure weight is the entire answer.
12 lbs of weight = 1 mph slower with the same power input (Schwinn tests).
A lot of 'classic frames' are not High Planers. So the compliance issue is only partially true.
I think the Varisities, et al, had slacker frame angles (more like RBW frames) and this MAY result in a different feeling when riding, compared to the higher "Italian" frame angles.
John Hawrylak
Woodstown NJ