Sure it's not easy, but the shots individually arent hard, syncing up all 3 in perfect timing is.
And ya, it's very much unlike actual shooting.
Oswald didn't have the chance to practice over and over, but he also didn't have a set of shots he was trying to match perfectly, so it was much easier for him.
Pulling off the correct shots in JFK reloaded is actually not that hard. The issue with getting a perfect 1000/1000 is how stupidly perfect your timing needs to be, down to the exact millisecond. The accuracy and ballistic trajectory of the bullet is easy comparatively.
Did you try backing the plywood with a piece of hardwood while drilling? If you can clamp the two together that will work even better.
Prop firearms are not really consumable items. They are just rented over and over again by production companies from rental companies. And when they break, the rental companies would first repair them before buying new ones. They could be decades old and have been repaired over and over.
I assume the shitty reliability of prop guns has more to do with their age and how much they are used rather than low manufacturing quality.