Actually, the time that Luke needed to train for a Jedi, didnt ever bother me untill the Prequels came and told us that training for a Jedi took like 20 years. But also, the prequels gave the Jedi much more power than what they had on the original trilogy.

The original Trilogy concept of a Jedi wasnt that much about The Superpowers, it was more about the person, and Luke was raised well by his uncles.

A standard Jedi would be like Obi Wan or Yoda, not really using their powers. They are more important as Who they are, leaders, masters, heroes, "Knights"

Luke is meant to be Powerful. The whole rescue on the Jabba's palace is meant to represent how centered he is and how much of a Leader he is and at the same time, to show how he could alone destroy the whole Jabba's crew.

What i mean, is that in the original trilogy concept of Jedi, it doesnt take THAT long to learn the philosphy of the Jedi code, you just need to face it and help you get centered (there is no need for learning tricks and combat style)