You can’t really compare one game to another when it comes to shooting in a first-person game (or any game really). They are all quite different.
If you just need to re-familiarize yourself with using a joycon or keyboard/mouse for gaming then find something simple(ish) to play with computer controlled characters (so you don’t get yelled at by other players). You won’t become great at the game that way (assuming you mean to do multiplayer) but you’ll get the feel for it all.
Once you have that down jump to multiplayer and know you will get whomped all over again till you get that learning curve sorted.
Sounds awful but it can be fun. Pretty much everyone has gone through it.
Use the right stick for pointing at roughly the correct place, then use the left stick (yep, move your character) to fine tune where your aiming dot is. This is especially useful in PvP mode because you’re moving around and harder to hit while you’re simultaneously zeroing in on your adversary. This works in every FPS game I’ve played, and it works in Skyrim as well. Takes a little practice to really get the hang of it, maybe 30 minutes or so.
If your target is moving, use the same technique to aim at where it is going, so you’re motionless when you fire. This actually works with real shotguns vs. clays as well.
BlackOps II (maybe the others) has a feature where you can play a map with bots ranging in skill from “mercifully untalented, possibly blind” to “impossible”.