Good equipment is very important. You can not shoot good targets without good equipment. Nope, sorry, it cannot be done. If your gun is shooting 4, 5, or 6 inch groups, you are going to have a lot of trouble putting together a good target. But if your gun is shooting 1 or 2 inch groups the opportunity for a good target is there, then it rests on the shooter.
Say you are an excellent shooter. You can hold 2 MOA. You are using a firearm that can only shoot 4 MOA. You will shoot 6 MOA on a target.
Not necessarily. You're assuming that the deviation from POA is cumulative, when in fact it may not be. It's just as possible the shooter's error could compensate for the rifle's error.
Not only that, but if you are a hunter, you're not shooting groups. It matters little where the second and third shots go at the range when you know that the rifle shoots to the point of aim, each and every time, on the first shot, when you're shooting at game.