I love that site too, and I have a treasured gift from my late father, a complete set of Handyman Encyclopedias. Which is essentially a hundred or more of these kinds of DIY plans.
One of my first projects as a teen was making a small sailboat out of pine and masonite. I got the main structure created ok, but I never got around to the crucial step of covering it with fiberglass, so it never saw water.
One of the biggest frustrations of trying to "go back" and do some of these now is the major changes in what's available, both in surplus/cheap components, and in hardware/supplies.
For surplus, at the time many of these were created (post WWII) , there was a lot of decent surplus equipment apparently going pretty cheap, and many of these projects actually specify what kind of surplus you should start with. And that's no longer the case. So you can still get ahold of the necessary components, but they're often more expensive than just buying the finished tool or object in question.
For supplies, these projects often specify items at the hardware store that are no longer sold. The only example that comes to mind is "Sal Ammoniac" but there are frequently things specified that the instructions assume are common and cheap, and they no longer are. And sometimes the project just uses some vernacular, some euphemism or trade name for an item that's no longer clear what the autor means.
But if you think of it more as general guidance of how to proceed, rather than step by step instructions, these things are still really handy to have around.
And if nothing else, they're just a lot of fun.
Another similar site is
https://www.countryplans.com/vintage_farm/index.html
There's some overlap, but I think there are some on countryplans that aren't on vintageprojects.
Bob
"Never be afraid to try something new. How hard can it be?"