Rubbish, maybe, but true.
Sure, the old mast might not work nearly as well as a new mast on your new sail.....but it works good enough for a better sailor to still sail better than YOU....and me...with tuning.
And a better sailor can still sail his 1999 mast and sail better than YOU for sure.
Heck, than me if course.
OTOH, maybe I sail 1999 sails better than YOU. Can you plane out of 70 % of your jibes on a typical 15-21 knot day? Can you stay dry that day after 50 jibes? And be the top 10% in speed also?
Not on a day sailing with PWA sailors, of course.