Not all cars are made equal. Just as you don't go to a cross-Sahara race in a car you don't know you, you don't buy a Prius to go logging in Alberta or Yakutsk.
Sure, that doesn't necessarily invalidate your argument, after all this increase in car complexity (through "electronization" and smartification of more and more components) without the increase in debuggability/repairability is IMHO a bad trade-off for many consumers.
Case in point, our second-hand 2011 Ford Focus has a problem with the electronic steering assist. Apparently it somehow experiences some kind of over-voltage and the internal system shuts down. It's likely due to humidity. (So probably it's simply a design/manufacturing/QA issue.) Okay, but there's no way to get the actual data from the integrated electronics from the steering system, but it's possible to reflash a different firmware on it. Which resets the internal data. Which basically clears this error state, and the car will happily use it.
But there's clearly a mechanical error, there's a new "bad" noise when turning the steering wheel. But it's a 10+ year car, rarely used, and replacing the steering system is about ~1000 EUR, doing the firmware flashing was ~30 EUR. (Finding the guy with the laptop, who can flash the firmware through the good old ODB port was the challenge.)
And it's basically a big (market) information asymmetry problem. The car industry wants to sell more cars. Sure they sell some parts, but the more repairability a car has the less parts it really needs, as consumers can make their own tradeoffs.