Thread drift -- I learned on a Remington Fieldmaster (572?) that belonged to a friend -- later my wife bought me a Remington Model 12 from about WW-1 that is still my squirrel rifle. Never shot either at paper except to check the sights, and didn't know what MOA was back when I started with them.... but I did hit what I was aiming at.
Accuracy for some of us is a "good enough" thing. If it isn't for you, well, so what?