Never had to debug a car I didn’t modify (and I’ve been modifying them for 40 years now).
Yea, when we add-on fuel injection or bigger turbos we alter the ECU. But daily drivers just don’t need debugging. Their failures are still mechanical systems (or sensors, which the computer then just uses defaults).
Automotive computers are some of the most rigorously tested tech out there. Even my 1974 Bendix analog fuel injection system has never “failed”. Components have, which then puts the system in fail-safe mode, like all automotive computers.
All the automation BS is another matter, which is why I refuse to own a car with that garbage. Like Tesla (or Mercedes and now upper-end of many brands). It’s simply not tested sufficiently, and I’m guessing it’s just not regulated like the “traditional” systems are.