The comp for an older generation is cars. Cars saw similar growth and adoption in the 50s-80s. And they had similar growing pains, reliability and maintenance issues were common place. So being able to perform maintenance and having an understanding of how they work was far more wide spread than just hobbyist and professionals.
As cars advanced the need to perform field maintenance and ad hoc repairs became less required so future generations (on average) became less knowledgeable and skilled at various car repair (and modification) activities, because cars just work now so there’s really no need to worry about learning how to fix minor issues, because they’re just not a common problem.
I think Anthony Jeselnik sums it up pretty well
https://youtu.be/4mCAl85hLkU?si=vwEMzE15kfHJMddV