Rebuilding a turbo is useful not as a single activity, but because there are a number of transferable skills involved. Way to think deep on that one.
Where messing with ancient junk fails is because it is obsolete. The person who did it, had to know how to do it already. They dont learn anything new by applying old knowledge to do something useless. The activity lacks the acquisition of transferrable skills and there is nothing useful created at the completion.
Not sure if you've noticed, but I'm going to die on this hill. You're more than welcome to be up here with me, but you may tire of the activity. I have IBS so I'm on the toilet a good bit, I have the time to keep going unfortunately.