I don't know, even if the "average person" wasn't rebuilding an engine, plenty of people were. Electronics and mechanics magazines and suchlike from back in the day were all geared towards doers and makers, now they're just geared towards wankers who sit on their asses and order a new Iphone every time they come across a story about the unbearable working conditions and suicides in Apple factories. I've got an '82 diesel VW Westfalia (with a '99 Jetta engine). Not only can I supplement many repairs with generic crap from a hardware store, I can also start it after an EMP and run it on rendered zombie fat. Or jet fuel. But more importantly, I can do all of the repairs myself--without any especially fancy equipment. Then we have a 2000-something Subaru somethingorother-wagon-thing, and changing a bulb in a headlight is an onerous task. It has this light that comes on when one of the tires' pressure is low--but it doesn't tell you which one! Unbelievable! Perhaps with older vehicles, most people couldn't tear down an engine and fix, but they could certainly do a hell of a lot more routine maintenance and basic repairs than they can do on pretty much any newer vehicle.