Ex teacher here. This was a common complain from other university departments.
We did not include debugging in the curricula, instead we taught debugging when a student got lost in their own code. Experience showed that was the moment they grok it the easiest. When they had their own code, their own baffling test case, and suddenly a new tool made it transparently easy to fix. They loved it immediately.
When we tried differently, the times we used to taught debugging in the whiteboard , it was a mess. Debugging requires carrying a lot of context line by line. Having 80 eyeballs watching the same debugging exercise, made the bug shallow and stole the aha experience from individual students.
This is very true. The whiteboard portions of the practical programming classes were among the most boring when I was going through school but actually trying to solve a problem myself was quite enjoyable and much better for learning. If I remember right we had a brief introduction to debuggers as a concept for better debugging but we were largely left to our own devices to figure out the features because everyone would need different things from it at different times.
It is the same like driving a car - you cannot teach someone driving a car by having a lecture, you also cannot teach someone driving a car when all they need is train line and they are happy with it.
Most of the discussion about "people not fit for the job" is mostly about if a person has real interest in topic to grind through and find their way around the topic.
I find people who are not interested in computers who suck at using them, but a lot of times it is only that they are not interested while having to use it for some things. All people that put effort and are interested get by quite well.
For me "demonstrate desirable difficulty" seems like "can't teach in a class setting" which in context of "why don't schools teach debugging" seems like "can't teach someone".
You most likely can teach someone in 1on1 setting and it would be easy to setup something to work together but that won't work at school. Even when we had laboratories at university there was not enough time to get everyone through laboratory exercise in smaller group than a lecture.
When we tried differently, the times we used to taught debugging in the whiteboard , it was a mess. Debugging requires carrying a lot of context line by line. Having 80 eyeballs watching the same debugging exercise, made the bug shallow and stole the aha experience from individual students.