Looking back 40 years, the boats then were well constructed.
In retrospect the rudder kick-up mechanism would tend to wear, but back then it was pretty cool and worked better than most. Hulls in those days weighed around 140 lb compared to 120 lb today. The cockpit was a little smaller and didn't have a storage compartment.
These days the care the boat has received over time way out shadows any shortcomings in design. The most major item found in any Sunfish..., probably in any boat, is a neglect to fix small leaks and subsequent waterlogging.