Spaghetti code isn't magic by my definition because there's a perfectly sensible methodology you can use to understand what it is doing based on the source code

Spaghetti code isn't magic by my definition because there's a perfectly sensible methodology you can use to understand what it is doing based on the source code, which is the same as whatever else you do to follow any other bit of code. The problem with spaghetti code is that the result that you obtain by following that methodology is incomprehensibly large. This is a different problem than not being able to come up with the result at all, or requiring more effort rather than less to come up with the incomprehensible mess. The result in both cases is incomprehensible code, and that can have similar downstream effects. But how you get there is different. And, of course, nothing stops a code base from being both highly magical and spaghetti code. There is no lower bound on code quality....