Joey's an Idiot!
At the beginning of the cemetary scene Swayze stands out in the middle and says "It's your mistake, Rossolini. When you set up my brother you forgot to kill me."
Then Joey says "That's why I'm here". He the nods to a guy who jumps out and sprays the cemetary with an Uzi.
If Joey had any brains and wanted the job done right he would have had a sniper complete the job with on shot. No wonder The Boss wanted to hand over the business to his son. Joey would have screwed up the whole family business.