What we consider substandard these days is not what was considered substandard 30 and 40 years ago, especially in mass production products. Starcraft has turned out a heck of a lot of boats over the years and a good many of them lasted a long time and are still going strong. That said, we learn new things and have new products every single year that will lengthen the time that something will last that we didn't have back then. How many of us 40 years ago would think we could drive a car over 400K miles and I have an Explorer that has 401,201 miles on it and I have rebuilt the engine a couple of times, first time at a bit over 200K and now I need to put new timing chains in it.
40 years ago, it was amazing to get 100K out of a car...
Materials available to us now a days are so much better than they used to be.