> cars used to break down much more often and require much more skilled maintenance.

Yeah, but “skilled maintenance “ was an easy skill. There could only be a handful of things wrong if it didn’t start: e.g. no spark, no fuel. In the case of no spark, you check the plug, see if it’s dirty, change it if so; check the distributor, maybe the points are bad; check the coil or condenser… yeah there were things to check, but you could actually fix it once you learned about it. And yes, you could do this on the side of the road—there were “tool rolls” you could have for such purposes.

Now, you get a check engine light and the code reader says, in so many words: “bring to dealer and pay up”