Maybe we'll have to chalk it up to my backwoods upbringing, but no - lining up a shot on an immobile target within effective range is damn near the level of difficulty I would declare "child's play". Heck, anecdotally speaking it was genuinely child's play when I first fire a shotgun at age 8 and hit my target (a spent shotgun shell 15 yards away) despite falling on my rear from not holding the shotgun quite right and also the first time I fired a revolver at some soda cans about 15 yards away and only missed on the first shot.
I'm not talking about military level practice, not even dedicated training, but guns do take some experience to fire accurately, even at stationary targets within effective range. If you are able to just pick up a gun, with no prior experience, and shoot with accuracy without at least a couple practice shots, you have very impressive eye-hand coordination. If you can hit a moving target from the get-go? You're probably a prodigy.
As for "use a different technique entirely" I have to completely disagree. You can, and should, be creating a solid eye-line aim no matter the type of firearm you are using - what's different is getting used to using a scope rather than using the sights built into the top of the weapon. The fact that a lot of people choose to shoot from the hip is just a lot of people choosing to completely ruin their own accuracy for no reason... just like a lot of real world thugs and thug wannabes started copying film and tv by holding their pistol sideways.
Sight vs Scope aiming isn't too different, in my experience. If you can master one, it isn't too hard to master the other. Spending the time to line up shot with a shotgun using the same technique as a rifle is counterproductive, particularly when hunting a moving target (like a dove or a rabbit). More important when firing a shotgun is the ability to quickly (not necessarily highly accurately) lead your target, a very different technique than an accurate shot at immobile or semi-mobile target (like a deer). Accuracy shooting with a rifle is very different than attempting to fire a shotgun or automatic weapon as they were intended to be used.
Attempting to fire a burst or automatic weapon is an entirely different experience. Learning to control recoil using small, controllable bursts takes time. Learning to, again, line up a shot quickly, instead of highly accurately, while still being able to hit your target takes time.
This method of quickly drawing a bead while leading your target is what I am referring to as "hipshooting". You simply don't have the ability to carefully line up a shot on a moving target. I can only imagine that this gets worse when you are moving as well.
If I had to split gun skills into categories, I would split them along the lines of Accuracte (Any weapon firing in Single/Semi-Auto mode, except shotguns and launchers), Rapid (Any weapon firing in Burst/Auto mode, plus shotguns), and Launcher (Launchers and related weapons)
small amount of firing weapons myself wouldn't say that it's too hard
Every tried to shoot a moving target, or try to aim under time constraints (deer might hear you and run)? When you have all the time in the world to aim at a target that moving, it's not too hard. Under pressure? Let's just say that there is a reason that average police accuracy hovers around 35%.