Alderaan said:
The original Star Wars was a combination of #2 and #3. Our perception of Luke’s strength and abilities grew over the course of the film, to the point where he was able to pilot his X-wing down the trench and fire the shot that blew up the Death Star
All Luke did with the exception of shooting a few Storm Troopers and blowing up Tie Fighters was a brief practice session with that droid. Going from that to blowing up the Death Star is pretty jarring.