say the interrupt h/w is not working for what ever reason - how does one attempt to debug this situation? Interrupts introduce a greater level of complexity - for an experienced person such as ourselves that is not that great an issue but for someone new to this kinda thing you just gotta keep it simple.
Testing an interrupt is as simple as setting the 'interrupt activating bit' in the emulator - or if you do not have one the simulator - that way you can fully test your ISR before even attempting 'live action'. Re your point "Interrupts introduce a greater level of complexity " a) I disagree since no loop timing issues exist and b) as above you can fully test before actvating. Many developers have tried to "avoid complexity" and tried to develop without the interrupts (that can come later) and found out they had to debug a loop timing problem which, of course, would not exist if interrupts had been employed in the first place.

Interrupts are our friends, not the enemy

Opinions may vary.
That they may.

Erik